UNIVERSITY  OF  ILLINOIS 

library 


book 


VOLUME 


Digitized  by  the  Internet  Archive 
in  2016 


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INTERNATIONAL 
LIBRARY  OFTECHNOLOGY 


A SERIES  OF  TEXTBOOKS  FOR  PERSONS  ENGAGED  IN  THE  ENGINEERING 
PROFESSIONS  AND  TRADES  OR  FOR  THOSE  WHO  DESIRE 
INFORMATION  CONCERNING  THEM.  FULLY  ILLUSTRATED 
AND  CONTAINING  NUMEROUS  PRACTICAL 
EXAMPLES  AND  THEIR  SOLUTIONS 


WORKING  CHILLED  IRON 
GEAR  CALCULATIONS 
GEAR  CUTTING 
GRINDING 

BENCH,  VISE,  AND  FLOOR  WORK 
ERECTING 
SHOP  HINTS 
TOOLMAKING 

GAUGES  AND  GAUGE  MAKING 
DIES  AND  DIE  MAKING 
JIGS  AND  JIG  MAKING 


SCRANTON : 

INTERNATIONAL  TEXTBOOK  COMPANY 

2-B 


Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Copyright,  1903,  by  International  Textbook  Company. 


Entered  at  Stationers’  Hall,  London. 


Working  Chilled  Iron  : Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Entered  at  Stationers’  Hall,  London. 

Gear  Calculations:  Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Copyright,  1903,  by  International  Textbook  Company.  Entered  at  Station- 
ers’ Hall,  London. 

Gear  Cutting  : Copyright,  1901,  by  The  Colliery  Engineer  Company.  Copy- 
right, 1903,  by  International  Textbook  Company.  Entered  at  Stationers’ 
Hall,  London. 

Grinding:  Copyright,  1901,  by  The  Colliery  Engineer  Company.  Entered  at 
Stationers’  Hall,  London. 

Bench,  Vise,  and  Floor  Work:  Copyright,  1901,  by  The  Colliery  Engineer 
Company.  Copyright,  1903,  by  International  Textbook  Company.  En- 
tered at  Stationers’  Hall,  London. 

Erecting:  Copyright,  190i,  by  The  Colliery  Engineer  Company.  Copyright, 
1903,  by  International  Textbook  Company.  Entered  at  Stationers’  Hall, 
London. 

Shop  Hints:  Copyright,  1901, by.THE  Colliery  Engineer  Company.  Copyright, 
1903,  by  International  Textbook  Company.  Entered  at  Stationers’  Hall, 
London. 

Toolmaking,  Parts  1-3:  Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Entered  at  Stationers’  Hall,  London. 

Toolmaking,  Part  3 : Copyright,  1903,  by  INTERNATIONAL  TEXTBOOK  COMPANY. 
Entered  at  Stationers’  Hall,  London. 

Gauges  and  Gauge  Making:  Copyright,  1901,  by  The  Colliery  Engineer  Com- 
pany. Copyright,  1903,  by  International  TEXTBOOK  Company.  Entered  at 
Stationers’  Hall,  London. 

Dies  and  Die  Making : Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Copyright,  1903,  by  International  Textbook  Company.  Entered  at  Sta- 
tioners’ Hall,  London. 

Jigs  and  Jig  Making:  Copyright,  1901,  by  The  Colliery  Engineer  Company. 
Copyright,  1903,  by  International  Textbook  Company.  Entered  at  Station- 
ers' Hall,  London. 


All  rights  reserved. 


\ 


lt2Ba 

BURR  PRINTING  HOUSE, 
FRANKFORT  AND  JACOB  STREETS, 
NEW  YORK. 


Q3.1.1 

V.  ZL.&opO 

l 


PREFACE 


The  International  Library  of  Technology  is  the  outgrowth 
of  a large  and  increasing  demand  that  has  arisen  for  the 
Reference  Libraries  of  the  International  Correspondence 
Schools  on  the  part  of  those  who  are  not  students  of  the 
Schools.  As  the  volumes  composing  this  Library  are  all 
printed  from  the  same  plates  used  in  printing  the  Reference 
Libraries  above  mentioned,  a few  words  are  necessary 
regarding  the  scope  and  purpose  of  the  instruction  imparted 
to  the  students  of — and  the  class  of  students  taught  by — 
these  Schools,  in  order  to  afford  a clear  understanding  of 
their  salient  and  unique  features. 

The  only  requirement  for  admission  to  any  of  the  courses 
offered  by  the  International  Correspondence  Schools  is  that 
the  applicant  shall  be  able  to  read  the  English  language  and 
to  write  it  sufficiently  well  to  make  his  written  answers  to 
the  questions  asked  him  intelligible.  Each  course  is  com- 
plete in  itself,  and  no  textbooks  are  required  other  than 
those  prepared  by  the  Schools  for  the  particular  course 
selected.  The  students  themselves  are  from  every  class, 
trade,  and  profession  and  from  every  country;  they  are, 
almost  without  exception,  busily  engaged  in  some  vocation, 
and  can  spare  but  little  time  for  study,  and  that  usually 
outside  of  their  regular  working  hours.  The  information 
desired  is  such  as  can  be  immediately  applied  in  practice, 
so  that  the  student  may  be  enabled  to  exchange  his 
present  vocation  for  a more  congenial  one  or  to  rise  to  a 
higher  level  in  the  one  he  now  pursues.  Furthermore,  he 

iii 


*>8216 


IV 


PREFACE 


wishes  to  obtain  a good  working  knowledge  of  the  subjects 
treated  in  the  shortest  time  and  in  the  most  direct  manner 
possible. 

In  meeting  these  requirements,  we  have  produced  a set  of 
books  that  in  many  respects,  and  particularly  in  the  general 
plan  followed,  are  absolutely  unique.  In  the  majority  of 
subjects  treated  the  knowledge  of  mathematics  required  is 
limited  to  the  simplest  principles  of  arithmetic  and  men- 
suration, and  in  no  case  is  any  greater  knowledge  of 
mathematics  needed  than  the  simplest  elementary  principles 
of  algebra,  geometry,  and  trigonometry,  with  a thorough, 
practical  acquaintance  with  the  use  of  the  logarithmic 
table.  To  effect  this  result,  derivations  of  rules  and 
formulas  are  omitted,  but  thorough  and  complete  instruc- 
tions are  given  regarding  how,  when,  and  under  what 
circumstances  any  particular  rule,  formula,  or  process 
should  be  applied;  and  whenever  possible  one  or  more 
examples,  such  as  would  be  likely  to  arise  in  actual  practice 
— together  with  their  solutions — are  given  to  illustrate  and 
explain  its  application. 

In  preparing  these  textbooks,  it  has  been  our  constant 
endeavor  to  view  the  matter  from  the  student’s  standpoint, 
and  to  try  and  anticipate  everything  that  would  cause  him 
trouble.  The  utmost  pains  have  been  taken  to  avoid  and 
correct  any  and  all  ambiguous  expressions — both  those  due 
to  faulty  rhetoric  and  those  due  to  insufficiency  of  statement 
or  explanation.  As  the  best  way  to  make  a statement, 
explanation,  or  description  clear  is  to  give  a picture  or  a 
diagram  in  connection  with  it,  illustrations  have  been  used 
almost  without  limit.  The  illustrations  have  in  all  cases 
been  adapted  to  the  requirements  of  the  text,  and  projec- 
tions and  sections  or  outline,  partially  shaded,  or  full-shaded 
perspectives  have  been  used,  according  to  which  will  best 
produce  the  desired  results.  Half-tones  have  been  used 
rather  sparingly,  except  in  those  cases  where  the  general 
effect  is  desired  rather  than  the  actual  details. 

It  is  obvious  that  books  prepared  along  the  lines  men- 
tioned must  not  only  be  clear  and  concise  beyond  anything 


PREFACE 


v 


heretofore  attempted,  but  they  must  also  possess  unequaled 
value  for  reference  purposes.  They  not  only  give  the 
maximum  of  information  in  a minimum  space,  but  this 
information  is  so  ingeniously  arranged  and  correlated,  and 
the  indexes  are  so  full  and  complete,  that  it  can  at  once  be 
made  available  to  the  reader.  The  numerous  examples  and 
explanatory  remarks,  together  with  the  absence  of  long 
demonstrations  and  abstruse  mathematical  calculations,  are 
of  great  assistance  in  helping  one  to  select  the  proper 
formula,  method,  or  process  and  in  teaching  him  how  and 
when  it  should  be  used. 

Four  of  the  volumes  of  this  library  are  devoted  to 
subjects  pertaining  to  shop  and  foundry  practice.  The 
present  volume,  the  second  of  the  series,  treats  on  the 
following  subjects:  working  chilled  iron,  gear  calculations, 
gear  cutting,  grinding,  bench  and  vise  work,  floor  work, 
erecting,  shop  hints,  toolmaking,  gauges,  dies,  and  jigs. 
All  these  subjects  have  been  treated  very  fully  and  every 
care  has  been  taken  to  represent  the  best  modern  prac- 
tice. The  papers  on  Grinding  will  serve  as  a guide  to 
those  who  operate  grinding  machines  and  also  to  manufac- 
turers in  selecting  wheels  best  adapted  to  the  work.  The 
papers  entitled  Bench,  Vise,  and  Floor  Work,  and  Erec- 
ting include  a thorough  treatment  on  the  subject  of  files 
and  filing,  laying  out  work,  and  the  various  types  of 
laying  out  plates,  and  the  erecting  of  various  classes  of 
machinery.  Special  attention  is  called  to  the  papers  bear- 
ing the  titles  Toolmaking,  Gauges  and  Gauge  Making, 
Dies  and  Die  Making,  and  Jigs  and  Jig  Making.  Each 
subject  has  been  treated  in  a very  thorough  and  exhaustive 
manner  and  should  prove  invaluable  to  any  one  interested 
in  toolmaking. 

The  method  of  numbering  the  pages,  cuts,  articles,  etc. 
is  such  that  each  subject  or  part,  when  the  subject  is 
divided  into  two  or  more  parts,  is  complete  in  itself ; hence, 
in  order  to  make  the  index  intelligible,  it  was  necessary  to 
give  each  subject  or  part  a number.  This  number  is 
placed  at  the  top  of  each  page,  on  the  headline,  opposite 


VI 


PREFACE 


the  page  number;  and  to  distinguish  it  from  the  page 
number  it  is  preceded  by  the  printer’s  section  mark  (§). 
Consequently,  a reference  such  as  § 37,  page  26,  will  be 
readily  found  by  looking  along  the  inside  edges  of  the 
headlines  until  § 37  is'  found,  and  then  through  § 37  until 
page  26  is  found. 


International  Textbook  Company. 


CONTENTS 


Working  Chilled  Iron  Section  Page 

Turning  Parallel  Rolls 7 1 

Turning  Rolls  With  Concentric  Grooves  7 9 

Grinding  Chilled  Rolls 7 17 

Corrugating  Rolls 7 20 

Planing  Chilled-Iron  Dies 7 23 

Gear  Calculations 

Gearing 17  1 

Spur  Gears 17  1 

Proportions  for  Gear-Teeth 17  8 

Rules  for  Spur-Gear  Calculations  ...  17  9 

Laying  Out  Teeth 17  17 

Involute  System 17  18 

Cycloidal  System 17  26 

Bevel  Gears 17  33 

Worm-Wheels  and  Worms 17  41 

Worm-Wheel  Calculations 17  44 

Worm  Calculations 17  46 

Gear-Cutting 

Systems  and  Processes 18  1 

Methods  and  Processes 18  2 

Duplication  System 18  5 

Formed-Cutter  Process 18  5 

Templet-Planing  Process 18  20 

Generation  System 18  22 

Conjugate-Tooth  Method*^ 18  22 

vii 


Vlll 


CONTENTS 


Grinding 

Section 

Page 

Introduction 

186 

1 

Grindstones  and  Oilstones  . 

18  6 

2 

Grinding  Wheels 

186 

7 

Abrasive  Materials 

186 

7 

Manufacture  and  Use  of  Emery 

Wheels 

186 

11 

Polishing  and  Buffing  .... 

186 

20 

Selection  of  Grinding  Wheels  . 

186 

25 

Hand  Grinding 

186 

27 

Hand  Surfacing  Machines  . 

186 

28 

Tool  Grinding 

186 

32 

Hand  Tool  Grinding  .... 

186 

32 

Machine  Tool  Grinding  . 

186 

34 

Machine  Grinding 

186 

41 

Grinding  Solids  of  Revolution  . 

186 

42 

Advantages  of  Grinding  . . . 

19 

1 

Selection  and  Use  of  Grinding  Wheel  . 

19 

3 

External  Grinding 

19 

16 

Internal  Grinding 

19 

37 

Surface  Grinding 

Cutter  and  Reamer  Grinding  . 

19 

45 

19 

47 

Purpose  of  Tool  Grinding  . 

19 

47 

Tool  Grinding  Machine  . 

19 

48 

Examples  of  Cutter  and  Reamer  Grinding 

19 

50 

Lapping 

19 

63 

Bench,  Vise,  and  Floor  Work 

Introduction 

20 

1 

Bench  and  Vise  Work  .... 

20 

2 

Tools  and  Fixtures  Employed  . 

20 

2 

Chipping 

20 

19 

Files  and  Filing 

20 

26 

Scrapers  and  Scraping 

21 

1 

Drills  and  Drilling 

21 

6 

Broaches  and  Broaching  . 

21 

9 

Reamers  and  Reaming  . 

21 

15 

Inside  Thread  Cutting  . . . 

21 

18 

Wrenches . 

21 

21 

CONTENTS  . ix 

Bench,  Vise,  and  Floor  Work — Con- 
tinued Section  Page 

Outside  Thread  Cutting 21  28 

Laying  Out  Work 21  36 

Subdividing  Circles 21  42 

Laying  Out  Plates 21  45 

Examples  of  Laying  Out 21  53 

Erecting 

Floor  Work 22  1 

Blocking 22  1 

Jack-Screws  and  Hydraulic  Jacks  ...  22  7 

Machine  Foundations 22  13 

Erecting  Floor 22  14 

Floor  Pits 22  19 

Use  of  Erecting  Pit 22  25 

Driving  Fits,  Press  Fits,  and  Shrink  Fits  22  29 

Hoists  and  Cranes 22  38 

Machine  Erection 23  1 

Lathe  Erection 23  1 

Planer  Erection 23  10 

Milling-Machine  Erection 23  20 

Engine  Erection 23  26 

Erection  of  a Horizontal  Stationary 

Engine 23  27 

Erection  of  a Vertical  Stationary  Engine  23  41 

Locomotive  Erection  ....  23  46 

Shop  Hints 

Rigging 24  1 

Pinch  Bars 24  2 

Use  of  Slings 24  3 

Use  of  Lashings 24  4 

Chain  Hoists 24  5 

Splices 24  6 

Knots,  Bends,  and  Hitches 24  11 

Erection  of  a Derrick 24  13 

Cleaning  Work  and  Castings  ....  24  18 


X 


CONTENTS 


Shop  Hints — Continued  Section  Page 

The  Soda  Kettle 24  18 

Pickling  Solutions 24  19 

Compressed  Air  for  Cleaning  ....  24  21 

Galvanizing 24  21 

Tinning 24  26 

Filling  and  Painting  Machine  Tools  . . 24  28 

Notes  on  Shop  Economy 24  28 

Cost  of  Construction 24  28 

Time  Element  in  Work 24  30 

The  Scrap  Heap 24  32 

Lubricants 24  35 

Lubricants  for  Reducing  Friction  ...  24  35 

Lubricants  for  Carrying  Away  Heat  24  41 

Power  Transmission 24  45 

Belting  and  Shafting 24  45 

Heat  Insulation 24  54 

Miscellaneous  Devices 24  56 

Babbitt  Metal 24  61 

Babbitting 24  62 

Useful  Information 24  69 

Toolmaking 

General  Tool-Room  Work 25  1 

Method  of  Procedure 25  1 

Dimensioning  Drawings 25  4 

Reading  Decimals 25  6 

Work  of  the  Toolmaker 25  7 

Measurements 25  8 

Limitations  of  Toolmaking 25  13 

Special  Tools  Used  in  Toolmaking  . . 25  14 

Cutting  Tools  and  Appliances  ....  25  21 

Design  and  Construction  of  Taps  ...  25  21 

Dies  for  Thread  Cutting 26  1 

Reamers 26  11 

Counterbores 26  35 

Hollow  Mills  . . 26  39 

Milling  Cutters 27  1 


CONTENTS 


xi 


Toolmaking — Continued  Section  Page 

Dividing  of  the  Circle 27  23 

Division  of  Lines 27  34 

Gauges  and  Gauge  Making 

Classification  of  Gauges 28  1 

Accuracy  Attainable  in  Gauge  Work  . 28  2 

Materials  Used  for  Gauges 28  4 

Gauge  Making 28  6 

Plug  and  Ring  Gauges 28  6 

Snap  Gauges 28  15 

Angular  Gauges 28  20 

Taper  Gauges 28  22 

Special  Gauges 28  42 

Dies  and  Die  Making 

Dies  and  Punches 29  1 

Classification  of  Dies 29  6 

Quality  and  Design  of  Dies 29  8 

Cutting  Dies 29  11 

Plain  Dies 29  11 

Progressive  Dies 29  15 

Compound  Dies 29  18 

Laying  Out  Dies 29  21 

Making  the  Die 29  27 

Different  Forming  Operations  ....  30  1 

Dies  for  Forming 30  2 

Bending  Dies 30  6 

The  Drawing  Process 30  13 

Drawing  Dies 30  15 

Size  of  Blanks  for  Drawing  and  Forming  30  26 

Redrawing  Dies 30  28 

Coining  Process 30  31 

Jigs  and  Jig  Making 

Classes  and  Use  of  Jigs 31  1 

Essential  Parts  of  Jigs 31  2 

Types  of  Jigs 31  2 


Xll 


CONTENTS 


and  Jig  Making — Continued 

Section 

Page 

General  Requirements  of  Jigs  . 

. 31 

3 

Jig  Details 

. 31 

6 

Guide  Bushings 

. 31 

6 

Clamping  Devices  ....... 

. 31 

12 

Stop-Pins 

. 31 

15 

Jig  Making 

. 31 

16 

Examples  of  Jig  Design 

. 31 

16 

Locating  Holes 

. 31 

26 

Locating  Holes  From  a Drawing  . 

. 31 

26 

Locating  Holes  From  a Model  . 

. 31 

31 

Marking  and  Recording  Jigs  . 

. 31 

33 

WORKING  CHILLED  IRON. 


TURNING  CHILLED  ROLLS. 


PARALLEL  ROLLS. 

1.  General  Consideration. — In  working  chilled  iron, 
good  results  are  only  possible  from  good  castings;  it  is 
necessary,  therefore,  to  see  that  the  castings  are  free  from 
cracks,  blowholes,  and  dirt,  and  that  the  chill  is  deep  enough 
so  that  the  metal  turned  off  will  be  of  even  hardness.  In 
turning  any  chilled-iron  rolls  it  is  necessary  to  employ 
special  lathes,  and  a few  general  rules  must  be  observed  in 
order  that  the  work  may  be  successful:  First,  the  cutting 
speed  must  be  so  slow  that  the  tool  will  hold  its  edge  until 
it  has  done  a reasonable  amount  of  work;  second,  the  tools 
and  machine  must  be  of  very  rigid  construction  and  have  a 
large  amount  of  power,  as  the  working  of  chilled  iron  pro- 
duces severe  strains  on  the  machine;  third,  the  tool  steel 
employed  must  be  a high-carbon  steel  tempered  as  hard  as 
fire  and  salt  water  can  make  it;  fourth,  the  operator  must 
be  patient  and  be  content  to  turn  off  fine  chips  that  very 
much  resemble  gray  hair. 

2.  Lathes  for  Turning  Parallel  Rolls. — Rolls  for 
flouring  mills,  calendering  rolls  for  paper  mills,  and  rolls  for 
similar  purposes,  in  which  a broad  flat  surface  is  required, 
are  frequently  turned  in  a special  type  of  lathe,  the  roll 
being  cast  as  a hollow  cylinder  chilled  on  the  outside.  This 

§7 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


WORKING  CHILLED  IRON. 


§7 


Fig. 


§7 


WORKING  CHILLED  IRON. 


3 


cylinder  is  turned  in  the  lathe  and  the  ends  cut  off,  after 
which  it  is  bored  and  fitted  on  a center  carrying  the  neces- 
sary shaft  and  journals.  Then,  in  the  case  of  flouring-mill 
and  calender  rolls,  it  is  ground  to  a perfect  finish  while  run- 
ning on  its  own  bearings.  Fig.  1 illustrates  a common  type  of 
roll-turning  lathe  with  the  roll  in  place.  In  this  style,  both 
spindles  are  made  hollow  and  the  roll  is  introduced  through 
the  spindles  and  held  by  setscrews  b passing  through  the 
collars  a.  In  the  style  of  lathe  shown,  both  spindles  are 
fitted  with  gears,  and  the  roll  is  driven  from  both  ends,  thus 
relieving  the  strain  on  the  lathe. 

It  will  be  noticed  that  this  style  of  lathe  is  not  provided 
with  a carriage  having  a feed  parallel  to  the  length  of  the 
lathe,  but  simply  with  a broad  tool  post  d fitted  upon  a 
cross-slide  c that  can  be  fed  along  the  ways  e by  means  of 
the  feed-screw  f.  A set  of  gearing  designed  to  give  the 
proper  speed  reduction  is  placed  on  the  end  of  the  lathe  at  j. 

3.  Lathes  driven  from  one  end  only  are  also  made  for 
this  work;  in  this  case,  the  tailstock  end  of  the  lathe  is  made 
with  a hollow  spindle  through  which  the  roll  can  be  intro- 
duced. Some  classes  of  rolls  have  narrow  necks  cast  on 
them,  and  in  this  case  the  rolls  are  held  during  turning  jn 
bearings  fitting  on  the  necks  in  the  same  manner  that  the 
rolling-mill  rolls  are  turned.  This  will  be  taken  up  in  con- 
nection with  the  description  of  the  turning  of  rolling-mill 
rolls. 


4.  Holding  and  Driving  the  Work. — Ordinarily,  in 
turning  10-  or  12-inch  rolls  that  are  to  be  bored  and  mounted 
subsequently,  the  roll  is  held  by  means  of  eight  setscrews  at 
each  end,  these  setscrews  also  acting  as  drivers.  Fig.  2 
illustrates  the  general  method  of  driving.  In  Fig.  1 can 
be  seen  the  collar  a through  which  the  setscrews  b are 
passed  to  hold  the  work.  The  same  letters  have  been  used 
for  referring  to  these  parts  in  Fig.  2.  The  roll  r is  centered 
and  held  by  means  of  the  setscrews  b.  This  method  of  ad- 
justing and  driving  the  roll  enables  the  workman  to  center 
the  chilled  part  very  carefully,  so  that  the  amount  of  turning 


4 


WORKING  CHILLED  IRON. 


§7 


required  will  be  as  little  as  possible.  There  is  generally 
about  -J  to  T3g-  inch  of  stock  to  be  turned  off  from  chilled 


rolls,  and  as  the  turning  process  is  very  slow  it  is  important 
that  the  centering  be  done  accurately  and  carefully. 

5.  Turning  Tools.  — The  tools  commonly  employed 
for  turning  parallel  rolls  are  flat  broad-nosed  or  wide-faced 
tools.  It  is  probable  that  \ in.  X 5 in.  x 5 in.  is  about  an  aver- 
age size  for  straight  work.  There  are  on  the  market  several 
brands  of  steel  made  especially  for  turning  rolls.  In  turning 
parallel  rolls  it  is  common  to  operate  two  tools  at  a time, 
thus  turning  10  inches  of  the  face  of  the  roll.  At  first 
thought  it  might  seem  best  to  use  one  tool  10  inches  wide, 
but  it  is  difficult  to  harden  so  wide  a tool  without  its  crack- 
ing; narrow  tools  are  far  less  liable  to  break,  and  on  the 
whole  there  is  greater  economy  of  steel  and  less  difficulty 
experienced  in  adjusting  tools  when  the  two  5-inch  tools  are 
employed  in  place  of  one  10-inch.  All  tools  for  turning 
chilled  iron  differ  radically  from  those  employed  on  softer 


b 


Fig.  2. 


§7 


WORKING  CHILLED  IRON. 


5 


metals,  and  all  the  turning  is  of  the  nature  of  scraping,  the 
tools  being  given  but  little,  if  any,  clearance.  Tools  for 
turning  chilled  iron  are  never  fed  into  the  work  and  then 
traversed  along  the  machine,  as  is  done  with  softer  metals, 
but  are  fed  straight  up  to  their  cut,  whether  turning  a par- 
allel face  of  a roll  or  the  bottom  or  the  side  of  a groove. 

6.  Grinding  Turning  Tools. — In  order  to  insure  a 
perfectly  straight  edge  on  the  tool,  it  should  be  ground  on 
a grinding  machine  provided  with  a a 

carriage  or  special  tool  holder.  The  ' 
tool  is  hardened  as  hard  as  fire  and 
salt  water  can  make  it  and  then 
traversed  across  the  face  of  an  emery 

wheel  to  make  the  face  a b of  the  tool  

concave,  as  shown  in  Fig.  3.  This 

’ Fig.  3. 

leaves  two  sharp  corners  a and  b. 

The  tool  is  first  set  to  use  one  corner;  when  this  becomes 


Fig.  4. 


6 


WORKING  CHILLED  IRON. 


§7 


dull  the  tool  is  turned  over  and  the  other  corner  utilized. 
Fig.  4 illustrates  a wet-grinding  emery  wheel  fitted  with  a 
slide  a upon  which  the  tool  can  be  clamped  at  b and  fed  back 
and  forth  across  the  face  of  the  emery  wheel,  the  different 
adjustments  being  obtained  by  means  of  hand  wheels  c 
and  d.  The  carriage  is  traversed  across  the  face  of  the 
emery  wheel  by  means  of  the  hand  wheel  e , which  operates 
a pinion  engaging  with  the  rack  f on  the  bottom  of  the 
carriage  a.  By  means  of  such  a device  as  this  the  tools  can 
be  accurately  and  quickly  ground. 

7.  Cutting-Off  Tools. — Special  cutting-off  tools  are 
employed  for  cutting  off  the  ends  of  the  chilled-iron  rolls 
after  the  bodies  have  been  turned  to  size.  Fig.  5 illustrates 
one  of  these  tools,  which  is  forged  from  f"  X steel  and 
tempered  by  dipping  into  salt  water.  The  edge  of  this  tool 
is  about  ||  inch  wide  and  the  corners  a and  b are  cut  off  at 


an  angle  of  45°,  as  shown.  Grinding  the  corners  in  this  man- 
ner prevents  the  breaking  of  the  sharp  corners  that  would 
otherwise  occur.  The  front  face  of  the  tool  is  given  a very 
little  clearance,  as  shown  at  c.  This  rarely  if  ever  amounts 
to  more  than  5°.  This  form  of  cutting-off  tool  is  employed 
simply  for  cutting  through  the  chilled  iron.  After  the 
softer  iron  at  the  center  of  the  roll  has  been  encountered,  an 
ordinary  cutting-off  tool  may  be  substituted  for  the  special 
one  shown. 


§7 


WORKING  CHILLED  IRON. 


7 


8.  Holding  the  Tools. — Owing  to  the  great  strain  to 
which  tools  employed  for  working  chilled  iron  are  subject,  it 
is  impossible  to  hold  them  in  any  ordinary  tool  post,  and, 
hence,  they  must  be  clamped  to  the  lathe  very  rigidly.  The 
ordinary  methods  for  holding  the  tools  for  turning  parallel 
rolls  are  clearly  shown  in  Figs.  1 and  2.  In  Fig.  2 the 
tool  c is  set  on  the  carriage  h and  clamped  down  by  means  of 
the  strap  e,  which  is  held  in  position  by  two  bolts  f.  The 
tool  is  forced  against  the  rolls  by  means  of  a series  of  set- 
screws g.  Care  must  be  taken  to  see  that  the  front  face  of 
the  rest  is  close  to  the  roll,  as  shown  at  i.  The  closer  this 
rest  is  to  the  roll,  the  less  danger  there  will  be  of  breaking 
the  front  face  of  the  tool.  The  flat  tools  employed  for  this 
work  may  be  originally  \ in.  X 5 in.  X 5 in.,  but  they  are 
subsequently  ground  parallel  to  one  axis  only.  If  the  tool 
is  ground  on  one  face  only,  but  two  cutting  edges  can  be 
obtained  from  one  grinding.  If  the  tool  is  ground  on  both 
edges,  as,  for  instance^*  and  k , four  cutting  edges  will  be 
obtained.  When  these  have  been  dulled,  the  tool  is  ground 
again,  and  each  succeeding  grinding  makes  it  narrower. 
Tools  can  be  used  until  they  become  so  narrow  that  they  can 
no  longer  be  held  by  the  clamps  e.  In  Fig.  1,  the  clamps 
cafi  be  seen  at  g\  in  this  case  very  narrow  tools  are  being 
employed  and  packing  pieces  h are  placed  behind  them  for  the 
setscrews  i to  bear  against.  The  upper  edge  of  the  tool  cf 
Fig.  2,  is  set  \ inch  below  the  center  of  the  10-inch  roll. 
This,  together  with  the  concave  form  of  the  face,  will  give 
the  proper  amount  of  clearance.  In  setting  cutting-off 
tools,  they  are  clamped  by  means  of  one  or  more  clamps 
similar  to  Fig.  2,  and  the  back  end  of  the  tool  is  set 
against  a setscrew  or  a packing  piece  held  by  two  or  more 
setscrews.  In  the  case  of  cutting-off  tools,  it  is  necessary 
to  have  them  overhang  the  front  edge  of  the  rest  i9  Fig.  2, 
to  a greater  extent  than  in  the  case  of  turning  tools,  and, 
consequently,  it  is  necessary  to  have  the  tool  deeper  from 
the  top  to  the  bottom,  so  that  it  may  be  stronger.  This  is 
why  the  cutting-off  tool  shown  in  Fig.  5 is  made  1J  inches 
deep,  and  as  the  top  face  d comes  above  the  center  of  the 


8 


WORKING  CHILLED  IRON. 


§7 

roll,  clearance  must  be  allowed  on  the  face  c,  Fig.  5.  After 
the  tools  have  been  clamped  in  place  they  are  fed  to  the  work 
by  means  of  the  feed-screw  f,  Fig.  1,  and  are  kept  parallel 
with  the  face  of  the  work  by  adjusting  the  setscrews  i.  The 
shavings  resemble  very  fine  needles  or  gray  hair. 

9.  Cutting  Speeds.  — The  cutting  speed  depends  to 
some  extent  on  the  character  of  the  chilled  iron  being 
turned,  the  character  of  the  steel  employed,  and  the  number 
of  machines  run  by  one  man.  In  the  case  of  job  work,  or 
where  one  man  has  to  give  all  his  time  to  a single  machine, 
it  pays  to  run  at  a comparatively  high  speed  and  sacrifice 
the  tools  more  rapidly,  thus  gaining  a greater  showing  for 
the  man’s  time;  but,  where  it  is  possible  to  have  matters  so 
arranged  that  one  man  can  operate  five  or  six  roll-turning 
lathes,  a speed  of  18  inches  per  minute  is  usually  considered 
best,  as  at  this  speed  the  tools  will  last  long  enough  to  do  a 
fair  amount  of  work,  and  as  they  remain  sharp  longer  they 
will  produce  a better  surface.  By  running  a number  of 
machines,  a man  is  able  to  turn  out  a good  day’s  work.  In 
some  cases,  where  a limited  amount  of  work  is  to  be  done 
and  time  is  an  important  factor,  work  is  run  as  rapidly  as 
3 feet  per  minute,  but  this  is  probably  the  maximum  speed 
at  which  good  work  can  be  done  on  chilled  iron. 

10.  Feed. — As  has  already  been  stated,  in  turning 
chilled  iron  a tool  is  never  fed  along  the  length  of  the  work 
but  at  right  angles  to  the  face  being  turned;  consequently, 
the  motion  that  corresponds  to  a feed  must  be  at  right 
angles  to  the  work.  When  turning  rolls,  the  feeding  is 
usually  done  by  hand  at  a rate  that  rarely  if  ever  exceeds 

inch  per  revolution.  A portion  of  the  surface  of  the 
roll  corresponding  to  the  faces  of  the  tools  in  action  is  turned 
to  the  required  diameter;  the  tools  are  then  reset  at  another 
place  and  another  part  of  the  surface  equal  to  that  already 
turned  is  finished. 

11.  Cutting  Off  the  Ends. — After  the  face  of  the 
roll  has  been  turned  to  the  correct  diameter,  it  is  cut  off  to 


§7 


WORKING  CHILLED  IRON. 


9 


the  proper  length  by  means  of  cutting-off  tools.  The  roll 
is  never  entirely  cut  off  on  the  lathe,  but  is  cut  down  until 
it  has  a narrow  neck  or,  in  case  the  roll  was  cast  hollow,  a 
shell  about  £ inch  thick  about  the  core;  it  is  then  removed 
from  the  lathe  and  iron  wedges  driven  into  the  cut  made  by 
the  cutting-off  tool  to  force  the  end  off.  In  case  the  roll  is 
to  be  bored  out  and  mounted  on  a bushing,  the  boring  is 
done  with  ordinary  tools  in  another  machine,  because  of  the 
fact  that  the  central  portion  is  soft. 


TURNING  ROLLS  WITH  CONCENTRIC 
GROOVES. 

12.  General  Consideration. — Rolling-mill  rolls  are 
practically  all  turned  with  concentric  grooves  or  with  con- 
centric rings  about  them,  these  rings  being  made  by  turning 
away  the  stock  between  so  as  to  leave  the  rings  projecting. 
Practically  all  rolling-mill  rolls  for  moderate-sized  work  are 
cast  in  a parallel  chill  and  are  chilled  to  such  a depth  that 
the  grooves  will  not  turn  through  into  the  soft  metal.  Roll- 
ing-mill rolls  may  be  divided  into  three  classes:  those  made 
of  chilled  iron,  called  chilled  rolls ; those  made  simply  of 
hard  iron  cast  in  a sanfl  mold,  called  sand  rolls ; and  those 
made  of  a mixture  of  cast  iron  and  steel,  called  sernisteel 
rolls.  The  two  latter  classes  are  not  so  hard  as  the  chilled 
rolls,  and  are,  therefore,  turned  in  a manner  more  nearly 
approaching  that  employed  in  the  turning  of  hard  castings. 
We  shall  here  deal  simply  with  the  turning  of  chilled-iron 
rolls. 


13.  The  Lathe. — The  exact  form  of  lathe  employed 
must  necessarily  depend  to  a large  extent  on  the  size  of  the 
rolls  operated  on.  Fig.  6 illustrates  a representative  type 
of  roll-turning  lathe.  It  will  be  noticed  that  the  lathe  is 
very  powerful,  and  is  provided  with  double  helical  gears,  so 
that  the  pull  may  be  constant  and  that  the  teeth  of  the 
gears  cannot  cause  hammering  or  backlash.  The  lathe  is 


Fig. 


§7 


WORKING  CHILLED  IRON. 


11 


provided  with  a short  carriage  a for  turning  the  bearings  or 
for  other  similar  work  when  it  is  necessary  to  traverse  the 
carriage  along  the  bed.  The  lathe  is  also  provided  with  an 
ordinary  tailstock  b having  a conical  center  c.  This  is  em- 
ployed when  turning  work  between  centers.  The  lathe  is 
made  very  rigid  and  its  bed  is  firmly  bolted  to  the  founda- 
tion. The  supports  d that  carry  the  tool  rest  e , together 
with  the  tool  rest,  are  made  very  rigid  and  massive,  so  that 
all  vibration  may  be  absorbed  and  there  may  be  no  lost 
motion  whatever. 

14.  Holding  the  Work. — When  the  casting  for  a roll 
first  comes  from  the  foundry,  it  usually  has  a large  riser 
head  on  one  end  that  has  to  be  cut  off.  This  is  ordinarily 
done  in  a regular  engine  lathe,  and  both  ends  of  the  roll 
shaft  are  trued  up  and  centered  in  the  lathe.  Care  must  be 
taken  to  true  the  roll  by  the  outside  of  the  chill,  so  that  dur- 
ing the  subsequent  turning  of  the  chilled  part  there  will  be 
the  least  possible  amount  of  stock  to  be  removed.  The 
surfaces  for  the  bearings  are  then  turned  with  the  roll  sup- 
ported on  ordinary  conical  centers  in  the  ends  of  the  roll 
shaft.  The  tailstock  b and  center  ct  Fig.  6,  may  be  em- 
ployed for  this  purpose,  a regular  center  being  introduced 
into  the  face  plate  /"and  the  bearing  turned  by  means  of  a 
tool  or  tools  supported  on  a carriage  a. 

15.  After  the  bearings  have  been  turned  either  in  the 
regular  turning  lathe  or  in  an  ordinary  engine  lathe,  the 
roll  is  mounted  in  special  housings,  as  shown  at  g and  h . 
The  lower  half  of  the  bearing  g is  supported  largely  on  the 
bridge  d that  extends  across  the  lathe  and  carries  the  tool 
rest  and  the  upper  half  of  the  bearing  li  is  made  adjust- 
able, one  end  of  it  being  secured  to  the  column  i by  means 
of  suitable  keys  j and  the  other  end  held  in  place  by  the 
bolt  k.  This  affords  ample  bearing  surface  for  the  support 
of  the  roll  during  turning  and  insures  the  turned  portion 
being  concentric  with  the  bearings.  The  roll  must  not  be 
rigidly  attached  to  the  face  plate  f,  but  is  driven  by  means 


12 


WORKING  CHILLED  IRON. 


§7 


of  a universal  coupling  /.  Sometimes,  in  order  to  take  up 
any  end  motion  of  the  roll,  a piece  is  placed  in  the  center  in 
the  end  m of  the  roll  and  the  other  end  of  the  piece  placed 
against  the  center  c,  thus  forcing  the  roll  toward  the  bear- 
ing  g and  taking  up  all  end  motion. 

16.  Turning  Tools. — The  turning  tools  employed  in 
turning  rolling-mill  rolls  do  not  differ  greatly  in  principle 
from  those  employed  in  turning  parallel  rolls;  but  in  most 
cases  the  amount  of  parallel  turning  is  considerably  less,  and 
cheaper  tools  can  be  used  for  the  purpose.  In  turning 
rolling-mill  rolls,  higher  and  stiffer  tools  must  be  used  for 
the  grooving  and  similar  work,  and  it  would  not  be  prac- 
ticable, therefore,  to  use  the  thin  tools  ordinarily  employed 
for  turning  the  surfaces  of  parallel  rolls,  as  the  cutting  edges 
would  be  so  far  below  the  center  of  the  roll  that  they  would 
have  an  excessive  amount  of  clearance  and  hence  become 
dull  very  quickly. 

17.  A good  form  of  tool  employed  for  surfacing  rolling- 
mill  rolls  preparatory  to  grooving  them  is  shown  in  Fig.  7. 
This  consists  of  a bar  of  steel  from  f inch  to  1 J inches 
square  with  four  grooves  cut  the  entire  length  of  the  bar 
along  the  middle  of  each  face,  as  shown.  The  tool  is  hard- 
ened as  hard  as  fire  and  salt  water  will  make  it,  and  is  then 


ground  flat  across  each  face,  thus  giving  four  cutting  edges, 
one  at  each  of  the  four  corners.  The  grooves  along  the 
sides  are  made  to  reduce  the  amount  of  grinding  necessary 
to  sharpen  the  corners.  Facing  tools  are  also  sometimes 
made  by  welding  a piece  of  flat  steel  to  the  face  of  a piece 
of  flat  iron  to  bring  the  thickness  up  to  an  inch  or  more, 
then  hardening  and  grinding  as  in  the  case  of  an  ordinary 
tool;  this  method  of  facing  cutters,  however,  is  not  as 


fig.  7. 


§7 


Working  chilled  iron. 


13 


advantageous  as  the  one  previously  given,  as  it  permits  of 
only  one  edge,  or,  at  the  most,  two  edges,  of  the  steel  being 
employed  as  cutting  edges. 

18.  Grooving  Tools. — For  all  grooves  having  a circu- 
lar cross-section,  very  efficient  grooving  tools  may  be  made 
by  turning  up  short  cylinders  of  tool  steel  to  the  desired  diam- 
eter, hardening  them,  and  grinding  the  ends  true.  One  of 
these  tools  is  shown  in  Fig-.  8.  When  it  is  desired  to  turn 
a groove  to  roll  ovals,  one  of  these 
circular  tools  is  simply  sunk  into 
the  face  of  the  roll  a short  dis- 
tance; when  it  is  desired  to  turn 
grooves  for  rolling  circular  rods, 
a tool  of  the  proper  diameter  is 
sunk  into  the  roll  to  half  of  its  depth.  These  tools  are 
ground  on  both  ends  and  can  be  used  in  at  least  four  posi- 
tions before  they  require  regrinding;  i.  e.,  both  the  front 
and  the  back  edges  at  the  top  and  the  bottom  can  be  used. 

19.  For  turning  rectangular  grooves  whose  sides  are 
either  parallel  or  perpendicular  to  the  length  of  the  roll,  a 
plain  rectangular  tool  similar  to  a cutting-off  tool  is  em- 
ployed, as  shown  in  Fig.  9.  These  tools,  when  narrow,  are 


i 

a 

b 

Fig.  9.  Fig.  10. 

made  wholly  of  steel;  when  wide,  they  may  be  made  partially 
of  steel  and  partially  of  iron,  as  shown  in  Fig.  10.  Apiece  of 
wrought  iron  a is  split  open  and  worked  out  on  the  end  to 


Fig.  8. 


14 


WORKING  CHILLED  IRON. 


§? 


receive  the  piece  of  steel  b , which  is  welded  into  the  wrought 
iron  and  hardened,  after  which  the  tool  is  ground  and  used 
as  though  it  were  a solid  steel  tool. 

20.  For  turning  rectangular  or  other  polygonal  grooves 
in  which  some  of  the  faces  of  the  grooves  are  neither  par- 
allel nor  perpendicular  to  the  axis 
of  the  roll,  it  becomes  necessary 
to  employ  tools  having  special 
forms.  For  roughing  out  grooves 
for  rolling  squares,  a tool  similar 
to  that  shown  in  Fig.  11  may  be 
employed,  this  tool  being  made  of 
a wrought-iron  body#  with  a steel 
cutting  face  b.  It  will  also  be  no- 
ticed that  the  point  c of  the  tool 

has  been  ground  off  to  reduce  the  liability  of  its  breaking. 
After  this  tool  has  been  sunk  into  the  groove  to  such  a depth 
as  to  give  the  groove  approximately  its  right  width  at  the 
surface  of  the  roll,  another  tool  having  a sharp  point  is 
introduced  to  remove  the  stock  left  by  the  point  c. 

21 . Sometimes  it  becomes  necessary  to  face  up  the  sides 
of  grooves,  in  which  case  a tool  of  the  style  shown  in  Fig.  12 
may  be  employed. 

This  tool  may  be 
made  of  solid  steel,  as 
shown  in  the  illustra- 
tion, or  may  be  made 
with  a piece  of  steel 
welded  to  the  top, 
as  shown  in  Figs.  10 
and  11.  It  will  be 
noticed  that  the  cut- 
ting edges  #,  b , and  c are  all  given  clearance,  so  that  the  tool 
can  cut  before  itself,  or  to  the  right  or  the  left. 

In  turning  irregular  grooves,  it  is  frequently  necessary  to 
make  formed  cutting  tools.  They  may  be  made  from  solid 


OJ 

Fig.  12. 


§7 


WORKING  CHILLED  IRON. 


15 


steel  or  by  welding  steel  on  iron,  as  shown  in  Figs.  10  and  11, 
and  then  grinding  the  cutting  edge  to  the  desired  form. 
Sometimes  the  cutting  edge  is  formed  to  approximately  the 
desired  form  before  hardening  the  tool.  The  tool  is  then 
hardened  and  the  cutting  edge  ground  to  fit  a templet  of 
the  desired  form. 

22.  Clamping  and  Holding  the  Tools. — The  tools 
employed  in  turning  rolling-mill  rolls  are  held  in  a manner 
very  similar  to  those  employed  in  turning  parallel  rolls,  it 
always  being  necessary  to  clamp  the  tool  as  firmly  as  possi- 
ble. The  rest  ^of  the  lathe  shown  in  Fig.  6 is  provided  with 
two  T slots  n and  with  rectangular  holes  in  its  upper  surface, 
as  shown.  These  rectangular  holes  are  fitted  with  dogs  o 
and  p.  The  dogs  o are  similar  to  the  ordinary  planer;  plug, 
as  shown  in  Fig.  13;  the  shank  a is  square  or  rectangular, 
depending  on  the  form  of  the  holes  in  the  rest  ey  Fig.  6.  In 


many  cases  these  holes  are  rectangular,  and,  consequently, 
the  point  a is  rectangular.  The  point  b of  the  setscrew  is 
brought  into  contact  with  the  tool  or  the  blocking.  The 
dog  /,  Fig.  6,  is  of  the  general  form  shown  in  Fig.  14,  and  is 
arranged  to  fit  into  a T slot,  as  indicated  by  the  dotted  lines. 
The  lug  a is  so  formed  that  the  dog  can  be  easily  removed 
from  the  T slot  by  simply  lifting  up  on  the  head  of  the  set- 
screw b , and  when  the  point  c of  the  setscrew  is  brought 
against  the  work,  it  will  cause  the  lug  a to  take  hold  of  the 
T slot  and  hold  the  work  firmly  in  place.  The  tools  are  held 


16 


WORKING  CHILLED  IRON. 


§7 


from  behind  and  at  the  sides  by  means  of  the  dogs  shown 
in  Figs.  13  and  14,  and  are  held  down  by  means  of  the 
clamps  or  setscrews  r in  the  clamp  s shown  in  Fig.  6. 


23.  When  tools  of  the  general  form  shown  in  Fig.  8, 
intended  for  turning  circular  grooves,  are  to  be  clamped, 
they  are  held  against  the  work  by  means  of  special  blocks 
provided  for  the  purpose,  as  shown  in  Fig.  15,  a being  the 


block  and  b the  cutting  tool. 


in  the  slot  in  the  end  of  the  piece  a. 
means  of  the  screw  r in  the  clamp  s , Fig.  6. 


A setscrew  is  brought  to  bear 
against  the  end  e of 
the  block  a to  crowd 
the  edge  c of  the  cut- 
ting tool  against  the 
work,  as  indicated  by 
the  dotted  lines  f g. 
The  tool  rest  d is  placed 
as  far  under  the  block  b 
as  possible,  and  in  some 
cases  no  clamp  is  placed 
on  top  of  the  block  b} 
the  resistance  along  the 
edge  c being  depend- 
ed on  to  hold  it  down 
against  the  rest  d and 
The  piece  a is  held  by 


24.  Allowance  for  Hot  Iron.  — In  turning  grooves 
for  rolling-mill  work,  it  is  necessary  to  make  the  grooves 
somewhat  larger  than  the  standard  bars  they  are  intended 
to  roll.  To  meet  these  requirements,  an  allowance  of 
inch  per  inch  is  usually  considered  sufficient.  For  in- 
stance, a tool  to  cut  a groove  for  rolling  a 1-inch  round  bar 
would  have  to  be  1^¥  inches  in  diameter,  and  a groove  for 
rolling  a 3"  X i"  flat  bar  would  have  to  be  3g3T  inches  wide, 
and  similar  allowances  would  be  required  for  all  shapes. 
All  the  tools  employed  in  roll  turning  may  be  finished  by 
grinding  after  tempering,  if  so  desired. 


§7 


WORKING  CHILLED  IRON. 


17 


GRINDING  CHILLED  ROLLS. 

25.  General  Consideration. — Chilled  rolls  intended 
for  use  in  flouring  mills,  calender  rolls  for  paper-making 
machinery,  and  rolls  for  rolling  some  classes  of  sheet  metal 
are  finished  by  grinding.  This  is  done  to  give  a smooth 
surface  and  to  insure  the  roll  being  parallel  throughout  its 
length. 

26.  Grinding  Machine.  — A machine  for  grinding 
flouring-mill  rolls  is  illustrated  in  Fig.  16.  The  roll  a is 
mounted  in  bearings  b so  that  it  is  rigidly  supported  and 
revolved  on  the  bearings  on  which  it  will  ultimately  work, 
thus  insuring  that  the  ground  surface  will  be  true  with  the 
bearings.  The  roll  must  be  driven  by  some  flexible  coupling 
so  as  to  allow  it  to  run  free  in  the  bearings  with  no  danger 
of  cramping  or  displacement.  This  is  accomplished  by 
means  of  the  universal  coupling  shown  at  c and  the  driving 
rod  d.  This  driving  rod  d extends  through  the  spindle  e of 
the  grinding  machine  and  is  secured  by  means  of  a universal 
joint  at  the  driving-wheel  end  of  the  spindle. 

The  grinding  is  done  by  means  of  two  emery  wheels 
mounted  on  opposite  sides  of  the  roll,  so  that  they  act  as  a 
pair  of  calipers,  the  roll  being  ground  between  them.  The 
emery  wheels  are  driven  by  belts  / /and  g,  g and  are  ad- 
justed by  means  of  hand  wheels,  one  of  which  is  shown  at  h. 
The  emery  wheels  are  supported  on  a carriage  i,  which  is 
traversed  backward  and  forward  on  the  bed  j so  that  the 
wheels  pass  over  the  entire  length  of  the  roll.  The  roll  is 
revolved  by  means  of  the  belt  k running  upon  a large  band- 
wheel  l shown  at  the  end  of  the  machine,  and  the  machine 
is  arranged  with  suitable  mechanism  for  traversing  the  car- 
riage automatically,  the  length  of  the  traverse  being  ad- 
justed by  means  of  stops.  The  emery  wheels  are  mounted  as 
shown  in  detail  in  Fig.  17.  The  emery  wheel  a is  supported 
on  a spindle  b provided  with  conical  endsr,  c.  These  conical 
ends  are  carried  in  Babbitt  bearings  </,  d.  Mounted  on  the 
spindle  b are  two  pulleys  e , e on  which  the  driving  belts  run. 


18 


WORKING  CHILLED  IRON. 


§7 


The  emery  wheel  is  surrounded  by  a suitable  hood  /.  The 
Babbitt  bearings  d are  turned  on  the  outside  to  fit  bearings 
in  the  frame,  as  shown  at  g,  g , and  the  adjustment  in  the 


direction  of  the  length  of  the  spindle  is  controlled  by  means 
of  the  yokes  h , h secured  by  studs  as  shown.  By  properly 
adjusting  the  bearings  d , all  end  motion  and  play  in  the 


Fig.  16. 


§7 


WORKING  CHILLED  IRON. 


19 


emery-wheel  spindle  can  easily  be  taken  up.  In  grinding 
chilled  rolls,  it  is  necessary  to  be  very  careful  about  the 
adjustments  of  the  emery  wheel  in  order  to  be  sure  that 
there  is  no  lost  motion.  The  clamp  yoke  h in  Fig.  17  is 
shown  at  m , Fig.  16,  and  the  end  of  the  Babbitt  bearing 
is  also  shown  at  n , while  the  guard  for  the  emery  wheel 


is  shown  at  o.  Rolls  of  larger  diameter,  such  as  large 
calender  rolls,  etc.,  are  frequently  ground  on  heavy  machines 
especially  manufactured  for  this  purpose  and  so  arranged 
that  the  emery  wheels  are  placed  in  a swinging  frame 
that  constantly  calipers  the  rolls.  This  is  known  as  the 
J.  Morton  Poole  grinding  machine,  which  is  described  in 
Grinding. 

27.  Grinding  Rolls.  — For  12-inch  rolls,  the  emery 
wheel  should  be  14  inches  in  diameter.  One  firm  manufac- 
turing a great  many  flouring-mill  rolls  employs  a No.  2 
grade,  grain  80,  carborundum  wheel,  though  any  wheel  of 
corresponding  grade  and  grain  may  be  employed.  If  the 
14-inch  wheel  is  employed,  it  should  be  given  about  1,600 
revolutions  per  minute,  and  a 12-inch  roll  should  be  given 
about  30  revolutions  per  minute. 

There  must  be  plenty  of  soda  water  running  on  the  wheels 
and  the  rolls  during  grinding,  to  keep  the  roll  cool  and  to 


20 


WORKING  CHILLED  IRON. 


§7 


carry  off  the  dust.  The  operator  adjusts  the  bearings  b , 
Fig.  16,  until  the  roll  is  in  perfect  alinement  with  the 
travel  of  the  carriage  i,  and  next  adjusts  the  emery  wheels 
to  take  equal  cuts.  The  emery  wheels  are  moved  up  by 
hand  as  the  roll  is  gradually  reduced  until  the  desired  size 
is  obtained. 

28.  Testing  Rolls. — If  the  rolls  are  properly  ground 
they  should  fit  perfectly,  and  in  order  to  test  them  an 

arrangement  similar  to  that 
shown  in  Fig.  18  is  employed. 
A small  carriage  a is  provided 
with  carefully  planed  paral- 
lels b and  c.  Two  rolls  are 
laid  on  these  parallels,  as  shown 
at  d and  e.  The  hose  f is  con- 
nected to  a gas  fixture  and  a 
series  of  gas  burners  are  ar- 
ranged on  the  pipe  g so  that 
they  furnish  a bright  light  back 
of  the  joint  between  the  rolls. 
If  the  work  has  been  properly 
done,  no  light  whatever  can  be 
seen  between  the  rolls,  as  they  rest  on  each  other  and  on  the 
parallels.  This  gives  an  extremely  delicate  test  of  the 
accuracy  of  the  workmanship  on  the  rolls. 


Fig.  18. 


PLANING  CHILLED  IRON. 


CORRUGATING  ROLLS. 

29.  General  Consideration. — Some  of  the  rolls  em- 
ployed in  flouring  mills  have  to  be  corrugated  after  they  are 
turned  and  ground.  The  corrugations  are  shallow  grooves 
planed  in  the  face  of  the  rolls;  they  are  not  parallel  to  the 


§7 


WORKING  CHILLED  IRON. 


21 


length  of  the  roll,  but  have  a slight  spiral.  These  grooves 
are  found  necessary  in  certain  classes  of  grinding  rolls,  not 
only  to  cause  material  to  feed  properly,  but  to  produce  the 
desired  result  upon  the  material  being  ground. 

30.  Corrugating  Machine. — The  machine  employed 
for  corrugating  rolls  is  similar  to  a planing  machine.  One 
type  of  this  class  of  machine  is  illustrated  in  Fig.  19,  in 
which  a is  the  roll  being  grooved.  The  weight  of  the  roll 
is  carried  on  suitable  bearings  b.  The  tailstock  c is  provided 
with  a center  that  takes  up  any  longitudinal  movement  of 


the  roll,  and  the  headstock  d is  provided  with  the  necessary 
mechanism  for  rotating  the  roll  through  the  proper  angle  to 
give  the  desired  spiral.  In  the  type  of  machine  shown  this 
is  accomplished  by  means  of  a worm-wheel  e and  a worm  f. 
The  worm  is  made  long  so  that  it  serves  as  a rack.  It  is 
controlled  by  the  slide  g traveling  in  the  slot  h.  This  slide 
carries  the  worm  across  the  grooving  machine  as  the  roll 


22 


WORKING  CHILLED  IRON. 


§? 


advances,  and  so  rotates  the  worm-wheel  e through  a por- 
tion of  a revolution  during  each  stroke  of  the  machine. 
The  proper  number  of  divisions  or  teeth  are  obtained  by 
means  of  an  automatic  spacing  device  shown  at  the  left- 
hand  end  of  the  worm-shaft  i.  This  spacing  device  gives 
the  shaft  i a portion  of  a revolution  after  each  stroke  of 
the  machine,  thus  advancing  the  cutting  tool  to  the  next 
groove. 


31.  Grooving  the  Rolls. — In  grooving  rolls,  a wide 
tool  similar  to  that  shown  in  Fig.  20  is  employed.  This 

tool  is  made  of  f"  x l?"  steel.  The 
tool  is  milled  on  the  end  with  the 
kind  of  corrugation  wanted,  after 
which  it  is  hardened.  The  tool  is 
so  set  in  the  machine  that  it  starts 
to  cut  on  one  side  and  each  suc- 
ceeding tooth  takes  a deeper  cut, 
until  the  last  one  finishes  the  cut 
to  the  required  depth.  This  rule 
holds  good  if  the  corrugations  are 
not  so  large  that  considerable 
metal  must  be  removed.  In  such 
cases  it  may  be  necessary  to  go 
around  the  roll  twice  to  finish  the  grooves.  In  ordinary 
practice  it  is  not  possible  to  take  a cut  of  over  inch 

in  planing  chilled  iron,  and,  unless  wide  tools  with  a num- 
ber of  teeth  are  employed,  it  will  take  a very  long  time  to  do 
the  grooving.  In  Fig.  20  the  curved  line  a b represents  the 
circumference  of  the  roll,  and  it  will  be  seen  that  each  suc- 
ceeding tooth  takes  a slightly  deeper  cut  than  the  preceding, 
the  tooth  c finishing  the  groove.  In  grooving  roils,  a speed 
of  approximately  24  inches  per  minute  is  usually  employed, 
and  in  some  cases  a speed  slightly  above  this.  One  reason 
why  a slightly  higher  speed  can  be  employed  in  grooving 
than  in  turning  rolls  is  to  be  found  in  the  fact  that  the 
grooving  tool  is  cutting  during  only  a portion  of  the  time, 
while  the  turning  tool  is  under  a constant  strain. 


§7 


WORKING  CHILLED  IRON. 


23 


PLANING  CHILLED-IRON  DIES. 

32.  General  Consideration. — It  is  frequently  neces- 
sary to  plane  chilled-iron  dies  for  pressed-brick  machines, 

swage  or  anvil  blocks,  drop-ham-  _____ 

mer  dies,  and  similar  purposes. 

This  work  may  be  accomplished 

by  making  the  speed  of  the  planer  i u ^ 

sufficiently  slow  and  the  tools  * 

sufficiently  rigid.  In  some  cases, 

dies  are  planed  by  feeding  a broad,  square-nosed  planing 
tool  directly  down  on  the  face  of  the  die,  a slight  amount  of 
feed  being  given  after  each  cut.  When  the  width  of  the 
tool  has  been  finished,  it  is  moved  along  and  a correspond- 
ing cut  taken  down  to  the  proper  depth.  This  method  of 
procedure  is  exactly  like  that  employed  in  turning  chilled 
rolls.  In  other  cases  a fairly  broad-nosed  planing  tool  is 
adjusted  so  that  it  will  act  both  as  a roughing  and  a finish- 
ing tool  and  is  given  a slight  feed  across  the  planer  after 
each  cut,  the  cutting  edge  of  the  tool  being  of  the  general 
form  shown  somewhat  exaggerated  in  Fig.  21;  the  por- 
tion a b is  parallel  to  the  surface  of  the  work  to  be  planed, 
and  the  portion  ac  is  inclined  so  that  it  will  act  as  a rough- 
ing tool  to  prepare  the  surface  for  the  finishing  cut.  Such  a 
tool  as  this  is  given  a very  slight  clearance.  It  is  possible 
to  follow  this  practice  of  feeding  sidewise  in  planing  where 
it  would  not  be  possible  to  do  so  in  lathe  work,  on  account 
of  the  fact  that  all  the  feed  occurs  at  the  end  of  the  stroke 
before  the  tool  begins  to  cut,  while  in  lathe  work  it  is  neces- 
sary to  feed  the  tool  sidewise  during  the  cut. 


GEAR  CALCULATIONS. 


GEARING. 


SPUR  GEARS. 


INTRODUCTION. 

1.  Object  of  Gearing. — Gearing  is  a term  sometimes 
applied  to  any  method  of  transmitting  motion  from  one 
shaft  to  another,  and  includes  all  such  combinations  as 
pulleys  and  belts,  rocker-arms  and  links,  and  toothed 
wheels.  It  is  the  object  of  gearing  to  transmit  power  or 
motion  with  as  little  loss  as  possible.  Many  of  the  problems 
relating  to  the  different  methods  of  transmission  are  similar, 
yet  each  method  has  its  separate  and  distinct  field  of  useful- 
ness. When  the  rotating  shafts  are  near  each  other  and  it 
is  desired  to  transmit  power  without  slipping  or  loss  of 
motion,  the  gear  has  its  greatest  usefulness.  The  two 
shafts  may  run  at  the  same  or  at  different  numbers  of 
revolutions  per  minute.  In  this  section  only  the  class  of 
gearing  known  as  toothed  gearing  is  dealt  with. 

2.  Velocity  Ratio. — The  number  of  revolutions  per 
minute  of  one  shaft  divided  by  the  number  of  revolutions 
per  minute  of  the  other  is  called  the  velocity  ratio.  Let 
two  wheels  with  parallel  axes  be  held  in  firm  rolling  contact 

§ 17 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 

C.  S’.  II.— 32 


2 


GEAR  CALCULATIONS. 


§17 


by  pressure  upon  their  axes,  as  in  Fig.  1.  If  one  wheel  be 
turned  in  either  direction,  and  there  is  no  slipping,  the 
other  wheel  will  rotate  in  the  opposite  direction  with  a cir- 
cumferential, or  surface,  velocity  equal  to  that  of  the  first; 
the  relative  motion  will  be  the  same  as  if  the  wheels  were 
connected  with  a crossed  belt,  and  the  numbers  of  their 


revolutions  will  be  inversely  proportional  to  their  circum- 
ferences or  to  their  diameters.  The  diameter  of  B being 
twice  the  diameter  of  A,  the  circumference  of  B is  twice  the 
circumference  of  A.  Hence,  when  B makes  1 revolution 
A must  make  2,  or  else  there  will  be  slipping  between 
A and  B. 

3.  Preventing  Slipping. — Should  slipping  occur,  B 
would  make  less  than  one-half  as  many  revolutions  as  A , 
assuming  A to  be  the  driver.  In  order  that  this  slipping 
may  be  prevented,  suppose  that  pieces  like  a , a , Fig.  2,  are 
fastened  at  equal  distances  on  the  peripheries  of  A and  B, 
and  that  corresponding  grooves  like  b , b are  cut.  Then,  the 
projections,  or  teeth,  on  one  wheel  will  run  between  the 
teeth  on  the  other,  and  B will  necessarily  revolve  with  the 


Fig.  l. 


GEAR  CALCULATIONS. 


3 


§ 17 

same  circumferential  velocity  as  A ; that  is,  on  each  gear 
the  same  number  of  teeth  will  pass  a given  point  in  a 


given  time.  When  a wheel  is  supplied  with  teeth  upon 
its  surface  it  is  called  a gear. 


DEFINITIONS. 

4.  The  following  definitions  are  important  and  apply  to 
all  the  principal  classes  of  gearing,  as  spur  gearing,  bevel 
gearing,  and  worm-gearing. 

A gear-wheel  or  gear  may  be  defined  as  a machine 
element  provided  with  projections  called  teeth , these  teeth 
being  so  formed  that  they  will  transmit  a definite  motion  to 
another  element  of  the  machine  by  engaging  with  similar 
projections  on  it.  When  the  projections  on  a pair  of  gears 
fit  into  one  another,  or  engage  one  another,  the  gears,  or 
their  teeth,  are  said  to  be  in  mesli. 

5.  A spur  gear  is  a gear  with  the  teeth  on  its  outer 
circumference  and  projecting  radially,  as  shown  in  Fig.  3. 
The  spur  gear  is  the  simplest  and  most  familiar  type  of  gear, 
and  the  principles  involved  in  the  formation  of  its  teeth 


4 


GEAR  CALCULATIONS. 


§17 


apply,  with  certain  minor  modifications,  to  the  formation  of 

the  teeth  of  nearly  every  type 
of  gear  in  common  use;  there- 
fore, a study  of  the  subject  of 
gear-teeth  can  best  be  begun  by 
a study  of  the  formation  of  the 
teeth  of  the  spur  gear. 

6.  The  pitch  cylinders 

of  spur  gears  are  the  imaginary 
cylinders  on  which  the  teeth 
are  constructed  and  that  roll 
together  with  the  same  relative 
speed  as  the  gears  themselves. 

7.  The  pitch  circle  of  a 


spur  gear  is  a circle  that  represents  the  pitch  cylinder.  The 


pitch  circle  is  shown  in  Fig.  4 in  its  relation  to  the  gear-teeth. 


§17 


GEAR  CALCULATIONS. 


5 


8.  The  pitch  diameter  is  the  diameter  of  the  pitch 
circle.  When  the  word  “ diameter  ” is  applied  to  gears,  it  is 

always  understood  to 
mean  the  pitch  diameter, 
unless  otherwise  specially 
stated,  as  outside  diame- 
ter,or  diameter  at  the  root. 


9.  The  distance  from 
a point  on  one  tooth  to 
the  corresponding  point 
on  the  next  tooth,  meas- 
ured along  the  pitch  cir- 
cle, is  called  the  circular 
pitch  ; it  is  obtained  by 
dividing  the  length  of 
the  circumference  of  the 
pitch  circle  by  the  num- 
ber of  teeth  in  the  gear. 
The  circular  pitch  is 
shown  in  Fig.  4. 

10.  Diametral 
pitch  is  the  number  of 
teeth  in  a gear  divided 
by  the  number  of  inches 
in  the  diameter  of  the 
pitch  circle.  It  has  also 
been  defined  as  the  num- 
ber of  teeth  in  a gear 
1 inch  in  diameter.  It 
is  obtained  by  dividing 
the  number  of  teeth  by 
the  pitch  diameter,  and 
hence  is  equal  to  the 
number  of  teeth  per  inch 

of  diameter.  A gear,  for  example,  has  60  teeth  and  is 
10  inches  in  diameter;  its  diametral  pitch  is  = 6,  and  the 


G 


GEAR  CALCULATIONS. 


§17 


gear  is  therefore  called  a 6-pitch  gear.  It  therefore  follows 
that  teeth  of  any  particular  diametral  pitch  are  of  the  same 
size  and  have  the  same  width  on  the  pitch  line,  whatever 
may  be  the  diameter  of  the  gear.  Thus,  if  a 12-inch  gear  has 
48  teeth,  it  will  be  4-pitch.  A 24-inch  gear  having  teeth  of 
the  same  size  will  have  twice  48,  or  96,  teeth — since  its  cir- 
cumference is  twice  as  long — and  its  diametral  pitch  is 
96  -r-  24  =.4,  the  same  as  before.  Fig.  5 shows  the  sizes  of 
teeth  of  various  diametral  pitches. 

The  diametral  pitch  multiplied  by  the  circular  pitch  of 
the  same  gear  equals  3.1416.  Using  for  illustration,  a 
wheel  10  inches  in  diameter  with  60  teeth,  we  have 


Circular  pitch  = 


circumference 
number  of  teeth 


10  X 3.1416 
60 


= .5236  inch. 


^ i i number  of  teeth  60  . 

Diametral  pitch  = ^ = — = 6. 

diameter  10 

The  product  of  the  two  is  6 X .5236  = 3.1416. 


1 1.  The  thickness  of  gear-teeth  means  the  thickness 
measured  on  the  pitch  circle,  as  shown  in  Fig.  4. 

12.  The  space  in  gear-teeth  means  the  space  between 
gear-teeth  measured  on  the  pitch  circle.  The  thickness  of  a 
gear-tooth  plus  the  space  equals  the  circular  pitch. 

The  addendum  is  the  part  of  a gear-tooth  outside  the 
pitch  circle,  as  shown  in  Fig.  4.  The  addendum  circle  is  a 
circle  through  the  extreme  outside  of  the  gear-teeth  ; its  diam- 
eter is  equal  to  twice  the  addendum  plus  the  pitch  diameter. 


13.  The  root,  or  dedendum,  is  the  part  of  the  teeth 
inside  the  pitch  circle,  as  shown  in  Fig.  4.  The  root  circle 
is  the  circle  that  limits  the  bottom  of  the  space  between  the 
teeth.  The  roots  of  the  teeth  are  usually  connected  to  the 
root  circle  by  a short  curve,  so  that  there  shall  be  no  sharp 
corner.  The  curve  that  fills  up  the  corner,  as  shown  in 
Fig.  4,  is  called  a fillet. 


14.  Backlash  is  the  side  clearance  between  two  teeth 
in  mesh;  it  is  equal  to  the.  difference  between  the  space  and 
the  thickness  of  a tooth,  measured  on  the  pitch  circle. 


§ 17  GEAR  CALCULATIONS.  7 

1 5.  The  clearance  is  the  space  between  the  top  of  a 
tooth  and  the  bottom  of  the  space  into  which  the  tooth 
meshes  when  they  are  on  the  line  connecting  the  centers  of 
the  gears.  It  is  equal  to  the  root  minus  the  addendum. 

16.  The  line  of  centers  is  the  straight  line  drawn 
from  the  center  of  one  gear  to  the  center  of  another,  with 
which  it  works  when  the  pitch  circles  touch  each  other.  The 
line  of  centers  passes  through  the  point  of  tangency  of  the 
two  pitch  circles. 

17.  The  pitch  point  of  a tooth  curve  is  the  point  in 
which  the  outline  of  the  tooth  intersects  the  pitch  circle. 
The  term  “pitch  point”  is  defined  in  books  on  machine 
design  as  the  point  of  tangency  of  the  pitch  circles  of  two 
gears  working  together.  The  first  definition,  however,  is 
more  in  accordance  with  the  use  of  the  term  in  shops,  and 
will  be  used  here. 

18.  The  face  of  a tooth  is  the  working  surface  of  the 
tooth  from  the  pitch  line  to  the  top  of  the  tooth;  the  flank 
is  the  surface  from  the  pitch  line  to  the  bottom  of  the  tooth. 

19.  The  length  of  a tooth  is  the  distance  from  root 
circle  to  the  addendum  circle;  it  is  equal  to  one-half  the 
difference  between  the  root  diameter  and  the  outside 
diameter. 

20.  The  breadth,  or  width,  of  a tooth  is  the  distance 
from  one  flat  surface  or  end  to  the  other,  or  the  distance 
from  one  top  edge  to  the  other  top  edge;  it  is  measured  at 
right  angles  to  the  length  of  the  tooth. 

21.  A gear  blank  is  the  cylindrical  piece  of  metal  or 
other  material  in  the  outer  circumference  of  which  gear- 
teeth  are  to  be  cut.  The  blank  is  turned  up  equal  to  the 
outside  diameter  of  the  gear,  and  the  teeth  are  then  cut 
about  its  periphery. 

22.  When  two  gears  are  so  located  that  their  teeth  run 
together,  the  gears  are  said  to  be  in  mesh. 


8 


GEAR  CALCULATIONS. 


§17 


23.  A rack  is  a gear  with  a pitch  circle  having  an 
infinite  radius,  that  is,  the  pitch  cylinder  has  become  a 
plane,  so  that  all  the  teeth  are  arranged  in  a straight  line. 

24.  A pinion  is  a small  spur  gear.  The  term  is  used 
especially  for  small  gears  that  mesh  with  racks. 


PROPORTIONS  FOR  GEAR-TEETH. 

25.  Gear-Teetli  Based  on  Circular  Pitch. — The 
relative  proportions  of  gear-teeth  are  usually  based  on 
the  circular  pitch.  It  is  customary  to  have  the  addendum, 
the  whole  depth,  and  the  thickness  of  the  tooth  conform  to 
some  arbitrary  part  of  the  circular  pitch.  There  is  no  uni- 
formly adopted  standard,  and  gears  made  in  different  ways 
require  different  proportions.  Cut  gears  require  less  back- 
lash and  clearance  than  cast  gears.  This  is  because  the 
teeth  of  cut  gears  are  more  uniform  in  size,  regular  in  out- 
line, and  truer  in  form  than  those  of  cast  gears.  Gears  of 
large  diameter  require  less  backlash  than  those  of  small 
diameter.  The  proportions  given  in  Table  I are  those  in 
common  use. 

TABLE  I. 


GEAR-TOOTH  PROPORTIONS. 


i 

2 

3 

4 

Addendum 

• 30  C 

.30  C 

.30  C 

1 *-P. 

Root 

.40  C 

.40  c 

•35  c 

1. 157  -5-  tO  I.I25'-f ■ P 

Working  depth  of  tooth 

.60  C 

.60  c 

.60  c 

2 + P 

Total  depth  of  tooth. . . 

.70  c 

.70  c 

.65  c 

2.157  "5-  P 

Clearance 

. 10  c 

.10  c 

.05  c 

.157  -4-PtO  .125  -h  P 

Thickness  of  tooth 

•45  C 

•475  C 

.485  c 

I.5I  -7-  P tO  I.57  -4-  P 

Width  of  space. 

• 55  C 

• 525  c 

• 515  c 

1.63  -T-  P to  I.  57  -T-  P 

Backlash 

.10  C 

.05  C 

.03  c 

,12  -r  /’tOO 

Recently  some  manufacturers  have  made  gears  with 
shorter  teeth  than  those  indicated  in  Table  I.  In  some 


GEAR  CALCULATIONS. 


9 


§ 17 

cases  the  total  depth  of  teeth  was  not  more  than  five-tenths 
the  circular,  or  1-|-  divided  by  the  diametral,  pitch.  The 
width  of  tooth  and  space  remained  the  same  except  that  the 
backlash  might  be  slightly  reduced. 

The  Brown  & Sharpe  Company  make  the  clearance 
one-tenth  the  thickness  of  the  tooth  on  the  pitch  line,  and 
The  Pratt  & Whitney  Company  make  it  one-eighth  the 
addendum. 

The  proportions  given  in  the  foregoing  table  have  been 
used  successfully  and  will  serve  as  an  aid  in  deciding  upon 
suitable  dimensions.  Column  1 is  for  rough  cast  gears 
where  the  teeth  are  very  irregular,  and  consequently  a large 
amount  of  backlash  and  clearance  is  required;  column  2 is 
for  the  better  class  of  cast  gears;  column  3 is  for  cut  gears; 
and  column  4 is  for  diametral  pitch  for  cut  gears.  C stands 
for  circular  pitch,  and  P for  diametral  pitch. 

26.  Proportions  of  Gear-Teeth  Based  on  Diam- 
etral Pitch. — As  the  gears  most  often  met  with  are  cut 
gears  of  diametral  pitch,  it  would  seem  natural  to  propor- 
tion gear-teeth  with  the  diametral  pitch  as  a basis.  It  is 
much  simpler  to  calculate  gears  using  diametral  pitch  than 
when  using  circular  pitch;  hence,  this  system  is  coming  into 
very  general  use  for  all  classes  of  gearing. 

Column  4 of  Table  I gives  the  proportions  of  gear-teeth 
based  on  this  system  as  used  by  the  leading  manufacturers 
in  this  country. 


RULES  FOR  SPUR-GEAR  CALCULATIONS. 

27.  Relation  Between  Circular  Pitch  and  Diam- 
etral Pitch. — The  product  of  the  circular  pitch  of  a gear 
and  the  diametral  pitch  is  always  the  constant  number 
3.1416.  Hence  the  following  rules  : 

Rule. — To  change  circular  pitch  to  diametral  pitch  divide 
S.lJf.16  by  the  circular  pitch. 

Example. — If  the  circular  pitch  is  .3927  inch,  what  is  the  diametral 
pitch  ? 


10 


GEAR  CALCULATIONS. 


S 17 


Solution. — Applying  the  rule  just  given,  the  diametral  pitch  is 


3.1416  _ 
.3927  ~ 


Ans. 


28.  R ule. — To  change  diametral  pitch  to  circular  pitch , 
divide  3. 1^16  by  the  diametral  pitch. 


Example. — If  the  diametral  pitch  is  4,  what  is  the  circular  pitch  ? 
Solution. — Applying  the  above  rule,  the  circular  pitch  is 


— — = .7854  in.  Ans. 

4 

20.  Relation  Between  Pitch  Diameter,  Number 
of  Teeth,  and  Diametral  Pitch.  — The  relation 
between  the  pitch  diameter,  number  of  teeth,  and  diametral 
pitch  is  expressed  in  the  following  ruies: 

Rule. — To  find  the  number  of  teeth  when  the  pitch  diam- 
eter and  the  diametral  pitch  are  known , multiply  the  pitch 
diameter  by  the  diametral  pitch. 


Example. — If  a wheel  is  30  inches  in  diameter  and  3 pitch,  how  many 
teeth  has  it  ? 

Solution. — Applying  the  rule  just  given,  the  number  of  teeth  is 
30  X 3 = 90.  Ans. 

30.  Rule. — To  find  the  pitch  diameter  when  the  num- 
ber of  teeth  and  the  diametral  pitch  are  known,  divide  the 
number  of  teeth  by  the  diametral  pitch. 


Example. — What  is  the  pitch  diameter  of  a 2^-pitch  gear  having 
20  teeth  ? 

Solution. — By  applying  the  rule  just  given,  we  find  the  diameter 
to  be 

20  0 . 

= 8 m.  Ans. 

31 . Rule. — To  find  the  diametral  pitch  when  the  number 
of  teeth  and  the  pitch  diameter  are  given,  divide  the  number 
of  teeth  by  the  pitch  diameter. 

Example. — If  a gear  contains  50  teeth  and  has  a pitch  diameter  of 
10  inches,  what  is  its  diametral  pitch  ? 

Solution. — Applying  the  rule, 


^ = 5 diametral  pitch.  Ans. 


GEAR  CALCULATIONS. 


§ 1? 


11 


32.  Finding  tlie  Outside  Diameter  of  a Gear- 
Blank. — The  diameter  to  which  the  blank  for  a spur  gear 
should  be  turned  is  equal  to  the  outside  diameter  of  the 
gear.  By  reference  to  Fig.  4 it  is  seen  that  the  outside 
diameter,  and,  hence,  the  diameter  of  the  blank,  is  equal  to 
the  pitch  diameter  plus  twice  the  addendum. 

With  the  diametral-pitch  system,  in  which  the  addendum 
is  equal  to  1 divided  by  the  pitch,  the  outside  diameter  may 
be  calculated  from  the  pitch  diameter  and  the  pitch  by  an 
application  of  the  following  rule: 

Rule. — To  find  the  outside  diameter , or  the  diameter  of  the 
blank , when  the  pitch  diameter  and  the  diametral  pitch  are 
known,  divide  1 by  the  pitch,  multiply  the  quotient  by  2,  and 
add  the  product  to  the  pitch  diameter. 

Example. — What  should  be  the  diameter  of  a gear-blank  for  a 
6-pitch  gear,  when  the  pitch  diameter  is  14  inches  ? 

Solution. — Applying  the  rule  just  given,  1 divided  by  the  pitch 
equals  1 6 = £ ; hence,  the  diameter  of  the  blank  is  found  to  be 

£ X 2 + 14  = 14.33  in.  Ans. 

33.  Since  the  pitch  diameter  is  equal  to  the  number  of 
teeth  divided  by  the  diametral  pitch,  and  the  addendum  is 
equal  to  1 divided  by  the  diametral  pitch,  the  sum  of  the 
pitch  diameter  plus  twice  the  addendum,  or  the  outside 
diameter  of  the  gear,  may  be  calculated  by  an  application 
of  the  following  rule: 

Rule. — To  find  the  outside  diameter , or  the  diameter  of  the 
blank,  when  the  diametral  pitch  and  the  number  of  teeth  are 
known,  add  2 to  the  number  of  teeth  and  divide  the  sum  by 
the  pitch. 

Example. — A wheel  is  to  have  48  teeth,  6 pitch ; to  what  diameter 
must  the  blank  be  turned  ? 

Solution. — By  the  rule  just  given,  the  outside  diameter  is 
48  -i-  9 

= 8.333  in.  Ans. 

34.  Calculations  Based  on  the  Outside  Diam- 
eter.— The  diameter  of  the  blank  and  the  pitch  being 


GEAR  CALCULATIONS. 


12 


§ 1? 


given,  the  number  of  teeth  may  be  calculated  from  the  fol- 
lowing rule: 

Rule. — To  find  the  number  of  teeth  when,  the  outside 
diameter  of  the  blank  and  the  diametral  pitch  are  known, 
multiply  the  outside  diameter  by  the  pitch  and  subtract  2 from 
the  product. 

Example. — A gear-blank  measures  10|  inches  in  diameter  and  is  to 
be  cut  4 pitch.  How  many  teeth  should  the  gear-cutter  be  set  to 
space  ? 

Solution. — By  applying  the  rule  just  given,  we  find  the  number  of 
teeth  to  be 

lOf  x 4 - 2 = 42  - 2 = 40  teeth.  Ans. 

35.  Rule. — To  find  the  diametral  pitch  when  the  outside 
diameter  and  the  number  of  teeth  are  known , add  2 to  the 
number  of  teeth  and  divide  the  sum  by  the  outside  diameter. 

Example. — It  is  required  to  select  a cutter  for  a gear  having 
54  teeth  that  is  to  mesh  with  the  change  gears  of  a lathe.  One  of  the 
change  gears,  which  has  64  teeth,  measures  6.6  inches,  outside  diam- 
eter ; for  what  pitch  should  the  cutter  be  selected  ? 

Solution. — Applying  the  rule  given,  the  pitch  of  the  change  gear 
64  + 2 

is  found  to  be  — — — = 10 ; hence,  this  is  the  pitch  of  the  cutter 
6.6 

required.  Ans. 


36.  In  applying  the  rule  given  in  Art.  35,  it  will  some- 
times be  found  that  the  result  obtained  does  not  correspond 
with  any  standard  pitch  number;  for  example,  a gear  with 
68  teeth  measures  inches  in  outside  diameter.  Apply- 

68  | ^ 

ing  the  rule  to  these  values,  the  pitch  would  be  - „ 

to.  o b2o 

= 4.4979-)-  ; this  number  is  so  near  to  4^,  which  is  a stand- 
ard pitch,  that  it  is  evident  that  4|  is  the  pitch  of  the  gear 
and  that  either  the  blank  was  not  turned  to  the  exact 
diameter  called  for  by  the  pitch  and  number  of  teeth  or  that 
the  exact  diameter  was  not  determined  by  the  measurement. 
When  a set  of  standard  gear-cutters  is  available,  the  pitch 
of  the  gear  can  also  be  determined  by  trying  different 
cutters  until  one  is  found  that  fits. 


GEAR  CALCULATIONS. 


13 


§17 

A considerable  difference  between  the  value  obtained  by 
applying  the  rule  and  the  nearest  standard  pitch  will  indi- 
cate that  an  uncommon  pitch  has  been  used.  In  general, 
however,  it  may  be  assumed  that  the  pitch  is  the  standard 
whose  number  agrees  most  nearly  with  the  value  obtained 
from  an  application  of  the  rule. 

As  far  as  practicable,  the  pitch  and  diameter  should  be  so 
chosen  that  the  number  of  teeth  will  cprrespond  to  a num- 
ber of  divisions  that  can  be  readily  obtained  with  the  aid  of 
the  indexing  mechanism  of  the  machine  in  which  the  gear 
is  to  be  cut. 


37.  Relation  Between  Pitch  Diameter,  Number 
of  Teeth,  and  Circular  Pitch. — If  any  two  of  the  fac- 
tors named  are  given,  the  other  can  be  found  by  applying 
one  of  the  following  rules: 

Rule. — To  find  the  diameter  of  the  pitch  circle  when  the 
number  of  teeth  and  the  circular  pitch  are  known , take  the 
continued  product  of  the  number  of  teeth,  the  circular  pitch , 
and  .3183. 

Example. — What  is  the  pitch  diameter  of  a gear-wheel  that  has 
75  teeth  and  whose  circular  pitch  is  1.625  inches  ? 

Solution. — Applying  the  rule,  the  diameter  is  found  to  be 

1.625  X 75  X .3183  = 38.79  in.  Ans. 


38.  Rule. — To  find  the  circular  pitch  when  the  pitch 
diameter  and  the  number  of  teeth  are  known , multiply  the 
pitch  diameter  by  3.11+16  and  divide  the  product  by  the  num- 
ber of  teeth. 


Example.  —What  is  the  circular  pitch  of  a gear  32  inches  in  diam- 
eter and  having  84  teeth  ? 


Solution. — Applying  the  rule  just  given,  the  circular  pitch  is  found 
to  be 


32  X 3.1416 
84 


1.1968  in.  Ans. 


39.  R ule. — To  find  the  number  of  teeth  zvhen  the  pitch 
diameter  and  the  circular  pitch  are  known , multiply  the  pitch 


GEAR  CALCULATIONS. 


14 


§17 


diameter  by  3.1Jf.lG  and  divide  the  product  by  the  circular 
pitch. 

Example. — How  many  teeth  will  there  be  in  a gear-wheel  25  inches 
in  diameter  if  the  circular  pitch  is  1.309  inches  ? 

Solution. — By  the  rule  just  given,  the  number  of  teeth  is 


25  X 3.1416 
1.309 


= 60. 


Ans. 


40.  Number  of  Teeth  and  Relative  Velocities. 

If  the  number  of  teeth  in  one  gear  and  the  number  of  teeth 
and  velocity  of  the  other  gear  of  a pair  of  gears  are  known, 
the  velocity  of  the  first  gear  may  be  found  by  applying  the 
following  rule  : 

Rule. — To  find  the  velocity  of  either  gear  in  a pair  of 
gears , when  its  number  of  teeth , the  velocity , and  the  num- 
ber of  teeth  of  the  other  gear  are  known , multiply  the  known 
velocity  by  the  number  of  teeth  in  that  gear  and  divide  the 
product  by  the  number  of  teeth  in  the  gear  whose  velocity  is 
required. 

Example. — At  how  many  revolutions  per  minute  will  a gear  with 
16  teeth  run  when  it  is  driven  by  a gear  having  72  teeth  and  running 
at  a velocity  of  30  revolutions  per  minute  ? 

Solution. — Applying  the  above  rule,  the  required  velocity  is  found 
to  be 

72  *x  30 

— — — - = 135  rev.  per  min.  Ans. 

41.  Velocity  Ratio. — When  comparing  the  velocities 
of  two  gears,  instead  of  considering  the  number  of  revolu- 
tions made  by  each  gear  in  a given  unit  of  time  as  1 min- 
ute or  1 second,  it  is  often  more  convenient  to  use  the 
ratio*  between  their  respective  velocities.  This  ratio  is 
called  the  velocity  ratio,  and  is  the  number  of  revolutions 
or  parts  of  a revolution  made  by  one  of  the  gears  for 
1 revolution  of  the  other.  Its  numerical  value  is  obtained 
by  dividing  the  number  of  revolutions  of  one  gear  in  a 


* By  ratio  of  two  numbers  is  meant  the  quotient  obtained  by  divi- 
ding one  number  by  the  other ; thus,  the  ratio  of  20  to  4 is  20  -s-  4 =,  5, 
and  the  ratio  of  4 to  20  is  4 -r-  20  = 


GEAR  CALCULATIONS. 


15 


§ 17 

given  time  by  the  number  of  revolutions  of  the  other  gear 
in  the  same  time,  the  number  of  revolutions  of  that  gear 
whose  velocity  ratio  is  sought  being  used  as  the  dividend. 
Instead  of  the  numbers  of  revolutions  in  a given  time,  the 
numbers  representing  the  diameters  or  number  of  teeth  may 
be  used  to  find  the  numerical  value  of  the  velocity  ratio,  in 
which  case,  however,  the  number  of  teeth  of  the  gear  whose 
velocity  ratio  is  sought  is  used  as  the  divisor. 

The  circumferences,  diameters,  and  numbers  of  teeth  are 
in  the  same  ratio,  but  they  are  inversely  as  the  velocity 
ratio. 

Example  1. — A pinion  makes  150  revolutions  per  minute  and  drives 
a gear  making  25  revolutions  per  minute.  What  is  ( a ) the  velocity 
ratio  of  the  pinion  with  respect  to  the  gear  ? ( b ) the  velocity  ratio  of 
the  gear  with  respect  to  the  pinion  ? 

Solution. — (a)  The  velocity  ratio  of  the  pinion,  that  is,  the  number 
of  revolutions  it  makes  while  the  gear  is  making  one,  is,  according  to 
the  foregoing  rule,  ^ = 6.  Ans. 

(b)  The  velocity  ratio  of  the  gear,  that  is,  the  number  of  revolu- 
tions it  makes  while  the  pinion  makes  one,  is  Ans. 

Example  2. — A gear  has  96  teeth,  while  the  pinion  meshing  with  it 
has  16  teeth.  What  is  (a)  the  velocity  ratio  of  the  pinion  ? ( b ) the 
velocity  ratio  of  the  gear  ? 

Solution. — ( a ) Dividing  the  number  of  teeth  of  the  gear  by  the 
number  of  teeth  of  the  pinion,  we  get  f£  = 6 as  the  velocity  ratio  of 
the  pinion.  Ans. 

(b)  In  this  case,  we  have  = i as  the  velocity  ratio  of  the  gear.  Ans. 

Example  3. — Two  gears  having  diameters  of  24  and  36  inches, 
respectively,  mesh  together ; what  are  their  velocity  ratios  ? 

Solution. — The  velocity  ratio  of  the  24-inch  gear  is  ff  = li;  that 
is,  it  makes  1 } revolutions  while  the  36-inch  gear  makes  1.  The 
velocity  ratio  of  the  36-inch  gear  is  § f = f ; that  is,  it  makes  f revolu- 
tion while  the  24-inch  gear  makes  1.  Ans. 

42.  Diameters  for  Fixed  Center  Distances. — The 

relations  between  the  diameters  of  gears  and  their  center 
distances  are  expressed  in  the  following  rules: 

Rule. — To  find  the  pitch  diameter  of  the  larger  gear  in  a 
pair  when  the  distance  between  centers  of  the  two  gears  and 


16 


GEAR  CALCULATIONS. 


§ 17 


their  respective  velocity  ratios  are  fixed,  multiply  twice  the 
distance  between  centers  by  the  velocity  ratio  of  the  smaller 
gear  and  divide  the  product  by  the  suni  of  the  velocity  ratios 
of  the  two  gears. 


Example. — The  smaller  of  two  gears  is  to  run  five  times  as  fast  as 
the  larger.  The  distance  between  centers  being  12  inches,  what  must 
be  the  pitch  diameter  of  the  larger  gear  ? 

Solution. — By  an  application  of  the  rule  just  given,  the  pitch  diam- 
eter of  the  larger  gear  is  found  to  be 


2 X 12  X 5 
5 + 1 


20  in'.  Ans. 


43.  Rule. — To  find  the  diameter  of  the  smaller  gear  in 
a pair  when  the  distance  between  centers  of  the  two  gears 
and  their  respective  velocities  are  fixed',  multiply  twice  the 
distance  between  centers  by  the  velocity  of  the  larger  gear  and 
divide  the  product  by'' the  sum  of  the  velocities  of  the  two 
gears. 


Example. — Taking  the  last  example  again,  what  should  be  the 
diameter  of  the  smaller  gear  ? 


Solution. — Applying  the  rule  just  given,  we  have,  as  the  diameter 
of  the  smaller  gear, 


2 X 12  X 1 
5 + 1 


4 in.  Ans. 


44.  Since  the  distance  between  centers  is  equal  to  the 
sum  of  the  radii  of  the  two  gears,  it  follows  that  when  the 
diameter  of  either  gear  has  been  calculated,  the  diameter  of 
the  other  may  be  found  as  follows: 

Rule. — To  find  the  diameter  of  one  gear  of  a pair  of 
gears,  when  the  distance  between  centers  is  fixed  and  the 
diameter  of  the  other  gear  is  known,  subtract  the  known 
diameter  from  twice  the  distance  between  centers. 

Example. — The  distance  between  centers  being  8 inches,  and  the 
diameter  of  One  gear  being  4 inches,  what  is  the  diameter  of  the 
other  gear  ? 

Solution. — Applying  the  rule  just  given,  we  obtain 
2x8  — 4 = 12  in.  Ans. 


GEAR  CALCULATIONS. 


17 


17 


LAYING  OUT  GEAR-TEETH. 


FORMS  OF  GEAR-TOOTH  OUTLINES. 

45.  Constant  Velocity  Ratio. — In  order  that  a tooth 
of  the  driving  gear  shall  press  on  a tooth  of  the  driven  gear 
in  such  a manner  as  to  produce  a constant  speed  of  turning 
while  they  are  in  contact,  it  is  necessary  that  the  curved 
outline  of  the  teeth  shall  be  constructed  according  to  a cer- 
tain law.  The  principle  involved  is  that  the  line  ik9  Fig.  6, 


fig.  6. 


called  the  normal  to  the  tooth  curves  at  their  point  of  tan- 
gency,  that  is,  the  point  where  they  touch,  must  pass  through 
the  point  of  tangency  of  the  pitch  circles  for  every  position 
in  which  the  two  teeth  are  in  contact.  When  this  condition 
is  satisfied  there  will  be  a constant  velocity  ratio  for  the 
gears. 

In  Fig.  6,  c and  d are  two  pitch  circles  with  their  respect- 
ive centers  at  a and  b.  The  curve  outlines  e and  /"represent 
the  teeth  of  two  gears  with  these  pitch  circles.  These  curves 
are  tangent  to  each  other  at  g,  and  h j is  a straight  line  tan- 
gent to  both  curves  at  the  point  g.  A line  perpendicular  to 
this  tangent  line  at  g is  the  normal  to  both  curves.  Such  a 
normal  k i passes  through  the  point  of  tangency  g of  the 
tooth  curves  and  the  point  of  tangency  / of  the  pitch  circles. 
The  curves  e and  /"are  so  designed  that  for  every  position 
in  which  they  can  be  in  contact  their  common  normal  passes 


C.  S.  II.— 33 


18 


GEAR  CALCULATIONS. 


§ 17 


through  the  point  of  tangency  of  the  pitch  circles.  These 
curves  therefore  satisfy  the  condition  for  constant  velocity 
ratio. 

46.  Devices  for  Drawing  Gear-Teeth. — An  odon- 
tograph is  an  arrangement  to  facilitate  the  laying  out  of 
the  curved  outlines  of  gear-teeth.  The  term  has  been 
applied  in  a number  of  different  forms,  but  its  application 
to  the  templets  for  laying  out  the  tooth  curves  seems  to  be 
the  best,  hence  many  persons  define  an  odontograph  as  a 
templet  for  laying  out  gear-teeth.  The  term,  however,  has 
also  been  applied  to  tables  that  give  the  radii  for  the  tooth- 
curve  outlines  of  gears,  though  it  would  seem  better  prac- 
tice to  call  these  odontograph  tables.  In  some  cases  the 
templet  has  to  be  used  in  connection  with  a table,  the  tem- 
plet being  simply  a means  for  finding  the  centers  from  which 
to  draw  the  tooth  curves. 

47.  Tooth  Curves  in  General  Use. — As  stated  in 
Art.  45,  the  motion  transmitted  by  one  gear  to  another 
will  be  smooth  and  uniform  only  when  the  teeth  of  the  gears 
are  given  definite  forms.  Theoretically,  the  number  of 
forms  that  meet  these  conditions  is  large;  practically,  how- 
ever, owing  to  the  necessity  of  simplicity  and  ease  of  con- 
struction, this  number  is  restricted  to  a few  simple  types, 
while  the  importance  of  uniformity  has  still  further  restricted 
the  types  in  common  use  to  two  general  systems,  known  as 
the  involute,  or  single-curve,  system  and  the  cycloidal, 
or  double-curve,  system.  Of  these  two  systems,  the 
involute  has  a number  of  important  advantages,  especially 
when  used  for  cut  gears,  that  are  constantly  bringing  it 
into  more  extensive  use,  and  many  of  the  best  authorities 
on  gearing  urge  its  universal  adoption  to  the  exclusion  of 
the  cycloidal  system. 


INVOLUTE  SYSTEM. 

48.  Definition  of  an  Involute. — Mathematically, 
an  involute  is  the  curve  that  would  be  drawn  by  a pencil 
point  at  the  end  of  a thin  band,  that  will  not  stretch,  and 


§17 


GEAR  CALCULATIONS. 


19 


that  is  drawn  tight  while  being  unwound  from  a cylinder. 
For  example,  suppose  such  a band  to  be  unwound  from  the 
cylinder  in  Fig.  7,  beginning  with  the  pencil  point  at  a on 
the  circumference.  As 
the  band  is  unwound,  the 
pencil  point  traces  the 
curved  line  a-l-2-S-Jf, 
etc.,  which  line  is  a part 
of  the  involute  of  the 
circle  that  represents  the 
circumference  of  the 
cylinder.  With  true  in- 
volute teeth,  the  path 
followed  by  the  point  of 
contact  of  the  tooth 
curves  of  the  teeth  on  the 
two  gears  is  a straight 
line,  called  the  line  of 
action,  that  is  tangent 
to  the  base  circles  of  both 
gears.  The  faces  of  involute  rack  teeth  are  straight  lines 
perpendicular  to  this  line  of  action.  In  practice,  the  base 
circles  are  usually  so  chosen  that  the  line  of  action  makes 
an  angle  of  15°  with  a line  that  is  tangent  to  both  pitch 
circles  at  their  point  of  tangency.  As  the  faces  of  the  rack 
teeth  are  perpendicular  to  the  line  of  action,  they  make  an 
angle  of  75°  with  their  pitch  plane.  In  the  approximate 
tooth  curves  frequently  used  in  practice,  the  faces  of  the 
rack  teeth  are  composed  wholly  or  partially  of  curves. 

49.  Base  Circle  for  Involute  Teeth. — The  base 
circle  in  the  involute  system  of  gearing  is  the  circle  to 
which  the  involute  that  forms  the  outline  of  the  tooth  is 
drawn.  The  radius  of  the  base  circle  is  smaller  than  that  of 
the  pitch  circle,  .the  difference  between  the  two  being  gen- 
erally found  by  multiplying  the  pitch  diameter  by  a number 
that  is  constant  in  any  given  system,  but  varies  somewhat 
with  different  systems.  For  most  purposes,  a difference 


20 


GEAR  CALCULATIONS. 


§17 


between  the  radii  of  the  two  circles,  or  a distance  between 
their  circumferences  D,  Fig.  8,  equal  to  -fo  of  the  diameter 
of  the  pitch  circle,  will  give  satisfactory  results.  Brown 
& Sharpe  use  a value  of  D slightly  smaller  than  this,  their 
rule  being  to  make  the  diameter  of  the  base  circle  equal  to 


\ 

\ 


\ 

\ 

\ 

\ 

\ 

w 

Fig.  8. 

the  product  obtained  by  multiplying  the  diameter  of  the 
pitch  circle  by  .968.  In  accordance  with  this  rule,  the  dis- 
tance D is  equal  to  the  diameter  of  the  pitch  circle  multiplied 
by  .016.  This  system  is  used  more  extensively  than  any 
other. 


50.  Example  in  Laying  Out  Teeth. — The  general 
method  of  laying  out  the  teeth  is  here  described  by  means  of 
an  illustrative  example:  Let  it  be  required  to  lay  out  the 
teeth  for  a gear  8 inches  in  diameter,  3 pitch.  By  the  pro- 
portions stated  in  column  4,  Table  I,  the  addendum  is  1 3 

= \ inch,  the  working  depth  is  2 X = f inch,  and  the 


GEAR  CALCULATIONS. 


21 


§17 

clearance,  using  The  Pratt  & Whitney  Company’s  propor- 
tions, is  -g-  X y = yt  inch.  By  Art.  49,  the  distance  from 
the  pitch  circle  to  the  base  circle  is  -g-1^  x 8 = T2T  inch.  First 
draw  the  pitch  circle,  see  Fig.  8,  with  a diameter  of  8 inches, 
then  draw  the  addendum  circle,  the  base  circle,  the  working- 
depth  circle,  and  the  root  circle,  making  the  distances 
A,  B , C , and  D , respectively,  -J,  and  T2^  inch,  in 

accordance  with  the  calculated  values.  If  no  scale  by 
means  of  which  these  fractions  can  be  laid  off  directly  is 
available,  they  may  be  reduced  to  decimals  and  laid  off  with 
a decimal  scale. 

The  pitch  being  3,  the  number  of  teeth  is  3 X 8 = 24. 
The  circumference  of  the  pitch  circle  must  therefore  be 
divided  into  24  equal  parts,  each  of  which  is  to  be  subdivided 
into  2 parts,  which  represent,  respectively,  the  thickness  of 
the  tooth  and  the  width  of  the  space  on  the  pitch  line.  The 
points  of  division  between  these  subdivisions  of  the  pitch 
circle  are  the  pitch  points  of  the  teeth ; the  outlines  of  the 
teeth  must  pass  through  these  points. 

The  work  is  now  ready  for  the  construction  of  the  tooth 
curves  between  the  base  circle  and  the  addendum  circle. 
These  curves  are  generally  circular  arcs  drawn  with  centers 
on  the  base  circle,  so  as  to  agree  as  closely  as  is  practicable 
with  the  theoretical  curves  for  the  tooth.  Two  methods  of 
drawing  them  are  described  in  the  following  articles. 

51.  Single-Arc  Approximation. — By  the  following 
method,  known  as  the  single-arc  approximation,  the 

outline  of  the  tooth  between  the  base  circle  and  the  adden- 
dum circle  is  the  arc  of  a circle  drawn  through  the  pitch 
point  with  a center  on  the  base  line  and  a radius  H,  Fig.  8, 
equal  to  one-fourth  the  radius  of  the  pitch  circle.  In  the 
example  under  consideration,  see  Art.  50,  the  radius  of  the 
pitch  circle  is  8 -s-  2 = 4 inches,  and  the  radius  H with  which 
to  draw  the  tooth  outline  is  4 X {■  = 1 inch.  When  the  num- 
ber of  teeth  is  greater  than  30  and  the  diametral  pitch  is 
not  less  than  10,  this  method  will  give  a curve  that  will  be 
satisfactory  for  most  ordinary  work.  With  larger  teeth, 


22 


GEAR  CALCULATIONS. 


§ 17 


TABLE  II. 


GRANT’S  INVOLUTE  ODONTOGR APH  TABLE. 


No.  of  Teeth. 

Divide  by  the  Diametral 
Pitch. 

Multiply  by  the  Circular 
Pitch. 

Face  Radius. 

Flank  Radius. 

Face  Radius. 

Flank  Radius. 

IO 

2.28 

.69 

•73 

.22 

II 

2.40 

.83 

.76 

•27 

12 

2.51 

.96 

.80 

•31 

13 

2.62 

I.09 

.83 

•34 

14 

2.72 

I . 22 

-87 

•39 

15 

2.82 

i-34 

.90 

•43 

16 

2.92 

1.46 

•93 

• 47 

17 

3.02 

1.58 

.96 

• 50 

18 

3.12 

1 . 69 

•99 

•54 

19 

3.22 

1.79 

1.03 

• 57 

20 

3-32 

1 . 89 

1.06 

.60 

21 

3-4i 

1 . 98 

1.09 

.63 

22 

3-49 

2.06 

1 . 11 

.66 

23 

3-57 

2.15 

1 • I3 

.69 

24 

3-64 

2.24 

1 . 16 

• 71 

25 

3.7i 

2-33 

1. 18 

• 74 

26 

3-78 

2.42 

1.20 

• 77 

27 

3.85 

2.50 

1.23 

.80 

28 

3-92 

2-59 

.1-25 

.82 

29 

3-99 

2.67 

1.27 

.85 

30 

4.06 

2.76 

1.29 

.88 

31 

4-13 

2.85 

1. 3i 

.91 

32 

4.20 

2-93 

i-34 

•93 

33 

4.27 

3.01 

1.36 

.96 

34 

4-33 

3-09 

1.38 

•99 

35 

4-39 

3.16 

1-39 

1 .01 

36 

4-45 

3-23 

1. 41 

1.03 

37-40 

4. 

.20 

1 . 

34 

41-45 

4-63 

1.48 

46-51 

5.06 

1. 

61 

52-60 

5. 

■ 74 

1. 

C<-> 

00 

61-70 

6. 

■ 52 

2.07 

71-90 

7. 

.72 

2. 

46 

91-120 

9' 

00 

t'' 

3- 

II 

121-180 

I3-38 

4- 

26 

181-360 

21 

. 62 

6. 

CO 

00 

GEAR  CALCULATIONS. 


23 


§ 17 


however,  and  especially  with  wheels  having  a small  number 
of  teeth,  the  curve  so  obtained  differs  considerably  from  the 
correct  curve  and,  in  these  cases,  more  satisfactory  results 
are  obtained  by  the  method  explained  in  the  following 
articles. 


52.  Grant’s  Involute  Odontograph  Table. — By 

this  method,  for  all  gears  having  fewer  than  37  teeth,  the 
curve  is  approximated  by  two  circular  arcs — one  extending 
from  the  pitch  circle  to  the  addendum  circle  and  the  other 
from  the  pitch  circle  to  the  base  circle — having  different 
radii,  the  center  of  the  arc  for  each  being  on  the  base  circle. 

The  lengths  of  the  radii  with  which  the  two  arcs  are  drawn 
are  obtained  by  the  following  method:  In  Table  II,  which  is 
taken  from  Grant’s  “Treatise  on  Gear-Wheels,”  are  two 
sets  of  numbers,  a part  of  each  set  being  in  two  columns. 
The  first  set  has  the  general  heading  Divide  by  the  Diame- 
tral Pitch  and  the  two  columns  in  this  set  have  the  respect- 
ive headings  Face  Radius  and  Flank  Radius.  This  set  is 
to  be  used  with  the  diametral-pitch  system.  To  find  the 
radius  F , Fig.  8,  for  the  face  of  a tooth  for  a gear  having  less 
than  37  teeth,  divide  the  number  in  the  column  headed 
Face  Radius,  opposite  the  number  that  corresponds  with  the 
number  of  teeth  in  the  gear,  by  the  diametral  pitch.  To 
find  the  radius  G of  curved  part  of  the  flank,  divide  the 
corresponding  number  in  the  column  headed  Flank  Radius 
by  the  diametral  pitch. 

The  second  set  of  two  columns  of  numbers  is  headed 
Multiply  by  the  Circular  Pitch  and  is  to  be  used  with  the 
circular-pitch  system.  It  is  used  in  the  same  manner  as  the 
first  set,  except  that  the  numbers  taken  from  the  table  are 
to  be  multiplied  by  the  circular  pitch. 

Applying  this  method  to  the  diametral-pitch  gear  of 
Art.  50,  in  which  the  number  of  teeth  is  24  and  the  pitch  3, 
we  proceed  as  follows:  To  find  the  radius  of  the  face,  we 
look  in  the  first  column  for  the  number  24  and  in  the  same 
horizontal  line  in  the  column  headed  Face  Radius,  we  find 
the  number  3.64,  which,  divided  by  the  pitch,  gives  us 


24 


GEAR  CALCULATIONS. 


§17 


3.64  -r-  3 = 1.21  inches  as  the  radius  A of  the  face.  In  the 
same  horizontal  line  and  in  the  column  headed  Flank  Radius, 
we  find  the  number  2.24;  this  number  divided  by  3 gives  us 
2.24  -f-  3 = .75  inch,  nearly,  as  the  radius  G of  the  flank. 

53.  Odontograph  Table  for  Gears  Having  More 
Than  36  Teeth. — An  inspection  of  Table  II  shows  that 
for  gears  having  more  than  36  teeth  there  is  but  one  column 
of  figures  under  each  of  the  respective  headings  of  diametral 
pitch  and  circular  pitch.  The  reason  is  that  the  whole 
curve  is  drawn  with  a single  radius,  whose  length  is  deter- 
mined by  the  general  method  already  explained.  It  is  con- 
stant for  all  gears  the  numbers  of  whose  teeth  are  included 
in  the  several  pairs  of  numbers  given  in  the  column  headed 
No.  of  Teeth;  for  instance,  the  length  of  the  radius  for  all 
numbers  of  teeth  from  37  to  40  is  determined  by  the  use  of 
the  numbers  in  the  horizontal  line  in  which  these  numbers 
occur. 

Example. — What  is  the  length  of  the  radius  for  the  curves  of  the 
teeth  of  a gear  having  64  teeth,  1.473  circular  pitch  ? 

Solution. — Since  the  number  of  teeth  lies  between  the  num- 
bers 61-70  in  the  first  column  of  the  table,  and  the  pitch  is  in  the  circu- 
lar-pitch system,  we  multiply  the  pitch  by  the  number  2.07,  which  is 
found  in  the  second  set  of  figures  at  the  right  of  the  numbers  61-70 
and  in  the  same  horizontal  row.  Performing  the  multiplication,  we 
get  1.473  X 2.07  = 3.05,  say  3 in.,  as  the  length  of  the  radius.  Ans. 

54.  Completing  the  Tooth  Outline. — With  any  of 
the  foregoing  methods  of  constructing  the  tooth  outline,  the 
flanks  of  the  teeth  are  radial  between  the  base  circle  and  the 
working-depth  circle;  this  part  of  the  outline  is  therefore 
made  to  coincide  with  the  straight  line  from  the  center  O of 
the  pitch  circle  to  the  point  where  the  curved  portion  of  the 
outline  intersects  the  base  circle,  as  is  shown  by  the  line  OI 
in  Fig.  8.  A fillet  from  the  working-depth  circle  connects 
the  radial  portion  of  the  outline  with  the  root  circle  and 
completes  the  outline  of  the  tooth.  Brown  & Sharpe  make 
the  radius  of  this  fillet  equal  to  one-seventh  the  width  of  a 
space  at  the  addendum  circle. 


GEAR  CALCULATIONS. 


25 


§17 

55.  Minimum  Number  of  Teeth. — The  smallest 
number  of  teeth  that  should  be  used  in  a cut  gear  whose 
teeth  are  laid  out  by  the  method  of  single-arc  approxima- 
tion is  30;  with  a smaller  number,  the  difference  between 
the  curve  obtained  by  this  method  and  the  correct  curve  is 
so  great  as  to  cause  the  teeth  to  work  unsatisfactorily.  By 
using  Grant’s  odontograph  table  in  the  manner  explained, 
it  is  possible  to  make  satisfactory  gears  that  have  as  few  as 
10  teeth. 

56.  Grant’s  Rule  for  Rack  Teeth. — The  teeth  of 
a rack  that  is  to  mesh  with  an  involute  gear  of  a given 
pitch  may  be  laid  out  by  the  following  method,  which  is 
known  as  “Grant’s  rule  for  rack  teeth.”  First  draw  the 
addendum,  pitch,  and  root  lines,  Fig.  9,  making  the  dis- 
tances A and  B each  equal  to  1 divided  by  the  diametral 


pitch,  and  the  distance  C equal  to  one-eighth  of  A.  On  the 
pitch  line  lay  off  the  pitch  distances  D,  D , and  divide  them 
into  the  two  parts  t and  s , corresponding,  respectively,  to 
the  thickness  of  the  teeth  and  the  width  of  the  spaces  on 
the  pitch  line.  Draw  the  sides  of  the  teeth  from  the 
working-depth  line  to  the  line  a a , which  is  drawn  half-way 
between  the  pitch  line  and  the  addendum  line,  as  straight 
lines  making  angles  of  15°  with  lines  that  pass  through  the 
pitch  points  perpendicular  to  the  pitch  line.  Draw  the; 
outer  half  of  the  addendum  as  a circular  arc  having  a 


26 


GEAR  CALCULATIONS. 


17 


radius  R whose  length  is  2.1  divided  by  the  diametral 
pitch,  or  .67  multiplied  by  the  circular  pitch.  A fillet  from 
the  working-depth  line  to  the  root  line  completes  the 
outline  of  each  side  of  the  tooth. 


CYCLOIDAL  SYSTEM. 

57.  Definition  of  a Cycloid.  — In  mathematics,  a 
cycloid  is  a path  described  by  a point  on  the  circumference 

of  a circle  as  the  circle  rolls 
upon  a straight  line;  thus,  the 
curve  a be,  Fig.  10  (a),  described 
by  the  point  b as  the  circle  j rolls 
along  the  line  a c is  called  a cycloid. 
The  circle  j is  called  a describ- 
ing, or  rolling,  circle.  When 
the  describing  circle,  as  h , 
Fig.  10  (b),  rolls  upon  the  out- 
side of  another  circle,  as  g,  the 
curve  e d described  by  any  point 
on  the  describing  circle,  as  e , is 
called  an  epicycloid.  If  the 
describing  circle,  as  i,  rolls  on  the  inside  of  another  circle, 
as  g,  the  curve  e f generated  by  any  point  of  the  describ- 
ing circle,  as  e , forms  what  is  called  a hypocycloid.  If  the 
circle  i has  a diameter  just  one-half  the  diameter  of  the 
circle  g,  the  hypocycloid  will  be  a straight  line,  or  a diam- 
eter of  the  circle  g.  If  the  diameter  of  the  circle  i is  less 
than  half  that  of  the  circle  g,  the  hypocycloid  will  have  a 
curve  as  shown  at  e f ’ while  if  the  diameter  of  i is  more  than 
half  the  diameter  of  g,  the  curve  will  extend  to  the  left  from 
the  point  e instead  of  to  the  right  of  e. 

58.  Laying  Out  Cycloidal  Teeth.  — The  pitch, 
addendum,  working  depth,  and  root  circles  are  drawn,  and 
the  pitch,  thickness  of  teeth,  and  width  of  spaces  on  the 
pitch  circle  are  laid  off  as  described  for  the  involute  system. 


fig.  io. 


GEAR  CALCULATIONS. 


27 


§ I? 

After  this  the  outlines  of  the  teeth  may  be  drawn  as  theo- 
retical curves,  but  the  more  common  method  is  to  draw  the 
curves  for  the  faces  and  flanks  as  circular  arcs  that  agree 
very  closely  with  the  theoretical  curves. 

59.  Grant’s  Cycloidal  Odontograph  Table. — One 

of  the  most  accurate  practical  methods  o£.  laying  out  the 
approximate  curves  of  cycloidal  teeth  by  means  of  circular 
arcs  has  been  devised  by  Mr.  George  B.  Grant.  The  lengths 
of  the  radii  of  the  arcs  and  the  location  of  their  centers 
are  determined  by  the  pitch  and  number  of  teeth  of  the 
gear,  in  conjunction  with  a table  of  factors  that  apply  to 
gears  of  all  sizes  from  a 10-tooth  pinion  to  a rack.  Any  two 
gears  with  teeth  of  the  same  pitch  and  length  laid  out  by 
this  method  will  work  satisfactorily  with  each  other.  The 
base  of  the  odontograph  table  is  a describing  circle  whose 
diameter  is  equal  to  the  radius  of  the  12-tooth  pinion;  a 
gear  laid  out  by  its  use  will  therefore  work  satisfactorily 
with  any  gear  having  the  same  pitch  and  general  tooth 
dimensions,  and  with  theoretical  cycloidal  curves  con- 
structed with  a describing  circle  whose  diameter  is  equal  to 
the  radius  of  the  12-tooth  pinion. 

GO.  Use  of  Grant’s  Cycloidal  Odontograph  Table. 

The  first  step  in  the  use  of  the  odontograph  table  is  the 
location  of  the  circles  on  which  lie  the  centers  of  the  arcs, 


Fig.  11.  These  circles  are  concentric  with  the  pitch  circle, 
and  their  distances  from  it  are  determined  in  the  following 
manner : In  Table  III,  which  is  taken  from  Grant’s  “ Treatise 


Divide  by  the  Diametral  Pitch.  Multiply  by  the  Circular  Pitch. 


28 


GEAR  CALCULATIONS. 


§17 


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17 


GEAR  CALCULATIONS. 


29 


on  Gear-Wheels,”  are  three  sets  of  numbers,  headed,  respect- 
ively, Number  of  Teeth,  Divide  by  the  Diametral  Pitch, 
and  Multiply  by  the  Circular  Pitch.  To  find  the  distance  A 
from  the  pitch  circle  at  which  to  draw  the  line  of  face  cen- 
ters for  a diametral-pitch  gear  with  a given  number  of  teeth, 
use  the  numbers  in  the  column  headed  Diametral  Pitch. 
Select  from  the  column  headed  Dis.  A,  under  the  heading 
Faces,  the  number  in  the  same  horizontal  line  as  the  num- 
ber corresponding  to  the  number  of  teeth  in  the  gear.  This 
number  divided  by  the  diametral  pitch  gives  the  distance  in 
inches  from  the  pitch  circle  to  the  circle  of  face  centers. 
The  distance  B from  the  pitch  circle  to  the  circle  of  flank 
centers  is  found  by  dividing  the  number  in  the  column 
headed  Dis.  B , under  the  heading  Flanks,  corresponding  to 
the  number  of  teeth  in  the  gear,  by  the  diametral  pitch. 

The  lengths  of  the  radii  C and  D of  the  arcs  forming  the 
outlines  of  the  faces  and  flanks  of  the  teeth  are  found  by 
dividing  the  numbers  in  the  respective  columns  headed 
Rad.  C and  Rad.  D,  corresponding  to  the  number  of  teeth, 
by  the  diametral  pitch. 

For  a circular-pitch  gear,  the  numbers  headed  Multiply 
by  the  Circular  Pitch  are  to  be  used.  The  numbers  are 
selected  as  in  the  diametral-pitch  system,  but  the  several 
distances  and  lengths  of  radii  are  found  by  multiplying  the 
numbers  in  the  table  by  the  circular  pitch. 

61.  Flanks  for  Gears  Having  lO  and  11  Teeth. 

The  numbers  in  the  table  for  the  flank  radii  of  gears  hav- 
ing 10  and  11  teeth  are  preceded  by  the  minus  sign  ( — ). 
This  indicates  that  the  direction  of  curvature  of  the  flanks 
is  opposite  to  that  of  the  gears  that  have  a larger  number  of 
teeth  and  that  the  centers  from  which  the  flanks  are  drawn 
must  be  taken  on  the  opposite  side  of  the  tooth.  The 
flanks  of  gears  having  a small  number  of  teeth  are  convex; 
those  having  a larger  number  of  teeth,  concave. 

The  flanks  for  gears  having  12  teeth  are  radial.  This  fact 
is  indicated  in  the  table  by  the  symbol  for  infinity  (co)  in  the 
columns  for  length  of  flank  radius  and  distance  from  pitch 


30 


GEAR  CALCULATIONS. 


§17 


circle  to  line  of  flank  centers.  To  draw  the  flanks  for  these 
teeth  draw  a straight  line  from  the  pitch  point  toward  the 
center  of  the  pitch  circle.  Then  draw  a fillet  from  the  point 
where  this  line  touches  the  working-depth  circle  to  the  root 
circle. 

G2.  The  Willis  Odontograph. — The  Willis  odonto- 
graph  is  a templet  by  means  of  which  the  radius  of  an 
approximate  circular  arc  is  obtained  for  drawing  the  outline 
of  gear-teeth.  The  form  of  templet  used  for  involute  teeth 


ib 

FIG.  12. 

is  shown  in  Fig.  12.  The  teeth  are  practically  the  same  as 
those  obtained  by  the  single-arc  involute  system.  The  two 
sides  of  the  odontograph  make  angles  of  75°  30'  with  each 
other.  One  side  is  divided  into  J-inch  graduations  marked 
from  1 to  15.  The  blank  side  is  placed  along  a radius  with 


GEAR  CALCULATIONS. 


31 


§17 

the  vertex  a on  the  pitch  circle.  To  find  the  radius  of  the 
tooth  face,  take  as  many  of  the  ^-inch  divisions  as  there  are 
inches  in  the  radius  of  the  pitch  circle.  If  the  radius  of  the 
pitch  circle  were  6 inches,  it  would  give  ac  as  the  radius 
of  the  tooth  face.  The  circle  of  centers  shown  dotted  is 
drawn  through  the  point  c on  the  reduced  scale  with  b c as  a 
radius,  and  the  tooth  curves  are  drawn  through  the  pitch 
points  of  the  teeth  previously  located  on  the  pitch  circle. 
With  fas  a center  the  tooth  curves*  h is  drawn,  and  with  d as 
a center  e f is  drawn,  giving  us  the  outline  of  the  tooth  space. 
Having  determined  the  circle  of  centers,  the  pitch  points, 
and  radius  for  tooth  curves,  the  rest  of  the  teeth  can  be 
readily  drawn.  A similar  templet  is  made  for  drawing 
cycloidal  teeth. 

63.  The  Robinson  Odontograph. — The  Robinson 
odontograph  is  formed  of  two  logarithmic  spirals ab  and  ac , 
Fig.  13,  one  being  the  evolute 
of  the  other.  They  are  used 
with  a table  prepared  by 
Professor  Robinson,  and  give 
a very  accurate  form  of  tooth 
outline.  The  part  of  the  curve 
used  is  almost  identical  with 
the  cycloid  up  to  gears  of 
6-inch  pitch. 

The  templet  is  made  so 
that  it  can  be  attached  to  a 
piece  of  thin  board  and  when  set  for  one  tooth  with  the 
board  centered  on  the  center  of  the  pitch  circle,  the  templet 
can  be  turned  to  any  desired  position,  and  the  outlines  of 
other  teeth  drawn.  In  Fig.  14,  a is  the  pitch  point  of  the 
tooth  and  b is  the  middle  point  of  the  same  tooth.  The 
line  be  is  tangent  to  the  pitch  circle  at  b and  the  line  ad  is 
tangent  to  the  pitch  circle  at  a.  From  the  table,  a number 
is  obtained  that  determines  the  number  on  the  odontograph, 
which  is  to  be  placed  at  the  pitch  point  a.  The  odontograph 
is  moved  around  this  point  until  the  curve  e is  tangent  to 


32 


GEAR  CALCULATIONS. 


17 


the  line  be.  When  in  this  position  the  face  af  of  the  tooth 
is  drawn.  The  odontograph  is  then  swung  around  the 
point  a until  the  same  curve  becomes  tangent  to  the  line  ad 


Fig.  14. 


when  the  flank  a g of  the  tooth  is  drawn.  When  one  tooth 
curve  has  been  formed  the  others  are  easily  made  by  attach- 
ing the  odontograph  to  a thin  board  fastened  at  the  center 
of  the  gear,  as  already  explained. 

64.  The  Walker  Odontograph  Chart. — Mr.  John 

Walker  designed  a system  of  curves  for  gear-teeth,  for 
which  he  prepared  a chart  giving  the  information  necessary 
for  drawing  the  curves,  thus  reducing  the  labor  of  laying  out 
the  gear-teeth.  This  system  is  used  in  a number  of  shops 
manufacturing  gearing  and  is  considered  by  many  the 
best  and  most  convenient  system  for  practical  use.  The 
form  of  tooth  he  uses  is  the  epicycloidal  for  the  face  and 
epitrochoidal,  or  approximate  hypocycloidal,  for  the  flank. 
The  tooth  curves  do  not  differ  greatly  from  the  regular 
cycloidal  form  already  explained.  By  means  of  the  chart, 
the  thickness  at  the  top,  pitch  line,  and  root  of  a tooth,  and 
the  radii  of  the  face  and  of  the  flank  can  be  determined  at 
once,  when  the  circular  pitch  and  number  of  teeth  of  a gear 
are  known. 


GEAR  CALCULATIONS. 


33 


§ 1? 


BEVEL  GEARS. 


INTRODUCTION. 


65.  The  teeth  for  ,the  spur  gear,  rack,  and  internal 
gear  are  made  on  the  same  principles.  They  are  all  simply 
a modification  of  the  spur  gear.  There  are  only  two  other 
forms  of  gears  that  are  of  sufficient  importance  to  require 
explanation  here;  they 
are  the  bevel  gear  and  the 
worm-gear . 

Bevel  gears  are  gears 
with  pitch  cones  instead 
of  pitch  cylinders.  The 
shafts  are  not  parallel, 
but  lie  in  the  same  plane. 

The  miter  gear  is  a 
special  case  of  bevel  gear 
in  which  the  shafts  are  at 
right  angles  and  the  gears 
have  the  same  number  of 
teeth  and  the  same  pitch 
diameter. 

66.  Rolling  Cones. 

It  has  been  explained 
that  the  motion  of  a pair 
of  spur  gears  with  cor- 
rectly formed  teeth  is  the 
same  as  that  of  two  cylin- 
ders having  diameters 
equal  to  the  pitch  diam- 
eters of  the  gears  and 
rolling  in  contact  with 
each  other,  without  slip- 
ping. In  a similar  way,  FlG-  15-  * 

the  motion  of  a pair  of  bevel  gears  is  the  same  as  that 
of  a pair  of  cones  rolling  together,  as  shown  in  Fig.  15. 


C.  5.  II.— 34 


34 


GEAR  CALCULATIONS. 


§ 17 


Fig.  16  represents  a pair  of  bevel  gears  in  which  the  roll- 
ing cones  are  in  contact,  so  that  if  the  teeth  were  continued 
all  around  the  gears,  the  latter  would  be  in  mesh.  The  pro- 
portions of  these  gears  are  so  chosen  that  their  relative 

motion  will  be  the 
same  as  that  of  the 
pair  of  rolling  cones 
in  Fig.  15.  The  re- 
lation between  the 
gears  and  their  cor- 
responding cones  is 
still  further  shown 
in  Fig.  16  by  the 
dotted  outlines  O ab 
and  O b c of  a pair  of 
cones  having  the 
same  dimensions  as 
those  in  Fig.  15. 


67.  The  Pitch 
Cones. — The  cones 
whose  relative  mo- 
tion corresponds  to 
that  of  a pair  of 
bevel  gears  are 
called  the  pitch 
cones  of  the  gears. 
The  pitch  circle  of 
a bevel  gear  is  the 
circle  represented 
by  the  base  of  its 
pitch  cone.  The 
diameter  of  a bevel 
gear  is  always  un- 
derstood to  mean  the  diameter  of  its  pitch  circle ; for  exam- 
ple, the  diameters  A and  B of  the  pair  of  gears  shown  in 
Fig.  16  are,  respectively,  the  diameters  ab  and  be  of  the 
bases  of  the  two  pitch  cones  O ab  and  O b c. 


§17 


GEAR  CALCULATIONS. 


35 


68.  Convergence  of  Bevel-Gear  Teeth. — In  nearly 
all  bevel  gears  found  in  practical  use,  the  pitch  cones  have  a 
common  apex  at  the  point  of  intersection  of  the  center  lines 
of  the  shafts  connected  by  the  gears,  and  the  axes  of  the 
cones  coincide  with  the  center  lines  of  these  shafts.  If 
the  teeth  of  such  gears  are  correctly  formed,  each  tooth 
surface  is  made  up  of  a series  of  straight  lines,  each  of 
which  passes  through  the  point  of  intersection  of  the 
center  lines  of  the  shaft,  or  the  common  apex  of  the  two 
pitch  cones;  the  teeth  of  a bevel  gear  may  therefore  be 
conceived  as  having  been  cut  out  by  a straight  line  that 
always  passes  through  the  apex  of  the  pitch  cone  while  it  is 
moved  in  contact  with  the  outlines  of  the  bases  of  the  teeth. 
For  example,  in  Fig.  16,  if  we  consider  a straight  line 
always  passing  through  O while  it  is  moved  in  contact  with 
the  outline  rstu  of  the  base  of  a correctly  formed  tooth,  the 
line  will  coincide  with  the  surface  m of  the  tooth  for  every 
point  of  its  motion.  On  account  of  this  convergence  of  the 
surfaces  of  the  teeth,  and  the  consequent  change  in  the  size 
of  the  tooth  curves,  it  is  impossible  to  correctly  form  either 
side  of  the  teeth  by  passing  a formed  cutter,  which  may  be 
either  a planing  tool  or  a milling  cutter,  but  once  over  the 
sides  of  each  tooth. 

69.  Bevel-Gear  Calculations.  — The  relations  be- 
tween the  pitch  diameters,  pitch,  numbers  of  teeth,  and 
velocities  of  bevel  gears  are  the  same  as  the  corresponding 
relations  between  the  same  features  of  spur  gears;  problems 
involving  these  relations  may  therefore  be  solved  by  an 
application  of  the  rules  for  spur  gears,  remembering  that  the 
diameter  of  each  of  the  bevel  gears  is  that  of  the  base  of 
its  pitch  cone. 


LAYING  OUT  BEVEL  GEARS. 

70.  Laying  Out  Pitch  Cones  When  the  Shafts  Are 
at  Right  Angles. — To  lay  out  the  pitch  cones,  first  the 
center  lines  oa  and  o b,  Fig.  17  ( a ),  of  the  shafts  are  drawn 
at  right  angles  with  each  other.  The  next  step  depends  on 
the  velocity  ratio,  or  on  the  relation  between  the  diameters, 


36 


GEAR  CALCULATIONS. 


§17 


or  the  numbers  of  teeth  of  the  two  gears,  and  the  conditions 
imposed  on  their  diameters,  or  their  distance  from  the 
point  of  intersection  of  the  center  lines  of  the  shafts. 


When  the  shafts  are  at  right  angles  to  each  other,  and 
the  diameters  of  the  gears  are  given,  or  can  be  calculated, 
the  points  r and  t are  obtained  by  laying  off  from  the  point 
of  intersection  o,  Fig.  17  {a),  a distance  on  each  line  equal 
to  the  radius  of  the  gear  on  the  other  shaft.  Through  the 
points  r and  t so  obtained,  the  perpendiculars  c d and  e d are 
drawn  intersecting  in  d.  Then  laying  off  r c and  t e equal, 
respectively,  to  r d and  t d and  drawing  the  lines  oc,  o d, 
and  o e,  the  outlines  of  the  pitch  cones  ocd  and  ode  are 
completed.  The  angles  coa  or  do  a,  and  eob  or  dob,  are 
called  the  center  angles  of  their  respective  cones. 

Example. — Lay  out  the  center  angles  of  a pair  of  bevel  gears  for 
the  shafts  whose  center  lines  are  o a and  ob.  Fig.  17  (a).  The  gears 
are  to  have  48  and  32  teeth,  respectively,  and  the  angle  between  the 
center  lines  is  90°. 

Solution. — Since  the  sizes  of  the  gears  are  proportional  to  the  num- 
ber of  teeth  in  them,  and  the  gear  on  the  shaft  oa  is  to  have  48  teeth, 


GEAR  CALCULATIONS. 


37 


§ 17 

while  that  on  o b has  32,  the  distances  to  be  laid  off  must  be,  respect- 
ively, 32  and  48  divisions  on  some  convenient  scale.  Therefore  by 
laying  off  on  o a a distance  o m equal  to  32  divisions  and  on  o b a 
distance  o n equal  to  48  divisions,  the  points  m and  n are  obtained 
through  which  the  lines  m s and  n s can  be  drawn  perpendicular, 
respectively,  to  the  center  lines  o a and  o b.  By  drawing  the  line  o s 
through  the  point  of  intersection,  s of  these  perpendiculars  and  the 
point  of  intersection  o of  the  center  lines,  the  center  angles  a o s and 
b o s of  the  pitch  cones  are  obtained.  Ans. 

7 1 . Laying  Out  Pitch  Cones  When  the  Shafts  Are 
Not  at  Right  Angles. — The  center  lines  of  the  shafts  are 
laid  out,  as  oa  and  o b,  Fig.  17  ( b ),  at  the  given  angle 
between  the  shafts,  and  any  convenient  distances,  as  o in 
and  on,  are  laid  off  on  them.  Through  the  points  in  and  n 
so  obtained,  lines  are  drawn  perpendicular  to  the  center  lines 
of  the  shafts,  as  7/^  and  n h,  that  are  proportional  either  to 
the  velocity  of  the  gear  on  the  other  shaft  or  to  the  diam- 
eter or  number  of  teeth  of  the  gear  on  the  shaft  from 
whose  center  line  the  perpendicular  is  drawn.  Then  through 
the  points  g and  h on  these  perpendiculars  draw  lines  par- 
allel to  the  center  lines  until  they  intersect  each  other.  The 
line  os  drawn  through  the  point  of  intersection  s of  these 
parallels  and  the  point  of  intersection  o of  the  center  lines  of 
the  shafts,  fixes  the  center  angles  do  a and  dob  of  the  gears. 

When  the  distance  from  the  point  of  intersection  of  the 
center  lines  to  the  base  of  one  of  the  cones  is  fixed  the  com- 
pletion of  the  cones  is  accomplished  by  laying  off  the  given 
distance,  as  or,  Fig,  17  ( b ),  on  its  proper  center  line. 
Through  the  point  r draw  the  line  c d perpendicular  to  oa, 
extending  it  until  it  intersects  the  line  os  in  d,  and  lay  off 
rc  equal  to  r d.  Through  d draw  the  line  de  perpendicular 
to  o b and  make  t e equal  to  t d.  Draw  c o and  e o.  The  out- 
lines of  the  two  pitch  cones  are  then  cod  and  doe,  respect- 
ively, and  the  pitch  diameters  of  the  two  gears  are  c d and  dc. 

When  the  diameter  of  one  or  both  of  the  gears  is  fixed,  the 
pitch  cones  may  be  laid  out  by  the  other  method  illustrated 
in  Fig.  17  ( b ).  First,  the  contact  line  os  is  laid  out  by 

the  method  explained;  then,  from  any  convenient  point, 
as  u,  on  the  center  line  of  the  gear  whose  diameter  is  given, 


GEAR  CALCULATIONS. 


38 


17 


a perpendicular  u v is  drawn  and  on  it  the  distance  u v is 
laid  off  equal  to  the  radius  of  the  gear.  Through  v , a 
line  v d is  drawn  parallel  to  o a until  it  intersects  the  contact 
line  os  in  d.  The  point  d will  be  one  extremity  of  the 
pitch  lines  of  the  gears.  From  d,  the  lines  dc  and  de  are 
drawn  perpendicular,  respectively,  to  the  axes  o a and  ob, 
making  the  distances  rc  and  t e equal,  respectively,  to  ? d 
and  t d;  from  the  points  c and  e the  lines  co  and  eo  are 
drawn.  The  outlines  of  the  pitch  cones  are  cod  and  doe. 

7'Z.  haying  Out  Bevel-Gear  Blanks. — The  method 
of  laying  out  the  blanks  for  a pair  of  bevel  gears  is  illus- 
trated in  Fig.  18.  First  the  pitch  cones  ocd  and  ode  are 
constructed.  On  the  lines  c o , do,  and  eo  the  distances  c c\ 
dd’  and  e e'  are  laid  off,  each  being  equal  to  the  length  of 
the  face  of  the  required  teeth.  Through  the  points  c and  c' , 
d and  d’ , e and  e\  representing  the  ends  of  the  teeth,  lines 
are  drawn  perpendicular  to  the  lines  oc , o d,  and  o e on  which 
these  points  are  located.  By  producing  the  lines  through  d 
and  d'  until  they  intersect  the  center  lines  oa  and  ob,  the 
points  f,  g , f and  g'  are  located. 

On  the  perpendicular  through  the  point  c,  the  distances  c k , 
cjr,  and  i' j'  are  laid  off  equal,  respectively,  to  the  adden- 
dum, root,  and  the  clearance  of  the  required  teeth,  calcu- 
lating these  values  from  the  pitch,  and  remembering  that 
the  pitch  diameter  is  the  diameter  cd  of  the  base  of  the 
pitch  cone.  Similarly,  the  distances  dh,  dj,  and  ij  are  laid 
off  representing  the  addendum,  root,  and  clearance  of  the 
tooth  of  the  gear  A,  and  the  corresponding  distances  di , dk, 
and  hk,  ei",  e k" , and  h"  k}'  of  the  teeth  of  the  pinion  B. 
From  each  of  the  points  so  determined,  a line  to  the  point  o 
is  drawn;  those  parts  of  these  lines  included  between  the 
perpendiculars  through  the  points  representing  the  ends  of 
the  teeth  give  the  outlines  of  the  teeth,  and  fix  the  outside 
diameters  hk  and  ii"  of  the  blanks. 

The  angles  oua  and  ovb  are  the  face  angles  and  lrca 
and  l"  e b are  the  edge  angles.  These  angles  are  used  in 
turning  up  the  blanks  preparatory  to  cutting  the  teeth.  In 
some  cases  it  may  be  more  convenient  while  turning  up  the 


GEAR  CALCULATIONS. 


39 


§ 1? 


blanks  to  work  from  the  angles  h'oa  and  i"ob\  when  the 
face  angles  are  given,  these  angles  may  be  found  by  sub- 
tracting the  corresponding  face  angles  from  90°.  The  cut- 
ting angles  i o a and  h"  o b are  used  for  setting  the  blank 
when  the  teeth  are  to  be  cut  in  the  milling  machine.  When 
the  gears  are  to  be  cut  by  planing,  the  angles  f o a and  b o k" 
are  taken  as  the  cutting  angles.  Since  the  lines  /'  h ' and  l"  i" 
are,  respectively,  perpendicular  to  the  lines  oc  and  o e,  the 
edge  angles  l’  c a and  l"  e b are,  respectively,  equal  to  the 
center  angles  coa  and  eob. 

73.  Determining  the  Angles  and  Diameters  of 
the  Blanks. — The  edge,  face,  cutting,  and  center  angles 
are  generally  determined  by  measuring  the  drawing  with  a 
protractor.  It  is  seldom  practicable  to  set  the  milling  ma- 
chine or  gear-cutter  to  angles  smaller  than  \ degree,  or  15'; 
it  is  therefore  useless,  in  most  cases,  to  attempt  to  measure 
the  angles  on  the  drawing  to  a greater  degree  of  precision. 

The  outside  diameters  of  the  blanks  may  generally  be  deter- 
mined with  a sufficient  degree  of  accuracy  by  measuring  from 
a carefully  made  drawing  like  that  of  Fig.  18.  It  is  better, 
however,  to  have  this  diameter  carefully  computed  in  the 
drawing  room  and  the  dimension  placed  upon  the  drawing. 

74.  Laying  Out  Tooth  Curves. — Having  the  pitch 
cones  and  the  side  outlines  of  the  teeth  laid  out,  Fig.  18,  arcs 
of  circles  are  drawn  with  radii  equal  to  the  distances  fj,fi , 
fd,  and  fh;  andgh,  gh,gd , and  gi  about  f and  g,  as  cen- 
ters, to  represent  the  roots,  working  depths,  pitch  circles, 
and  addenda  of  the  teeth  at  the  larger  end.  These  arcs  are 
on  the  drawing  on  which  the  blanks  are  laid  out,  but,  if 
desirable,  they  may  be  made  on  separate  sheets.  They  are 
used  in  laying  out  the  tooth  curves  in  the  same  manner  as 
the  similar  circles  for  spur  gears  are  used. 

In  explaining  the  use  of  these  arcs  for  laying  out  the  teeth, 
the  circle,  of  which  the  arc  representing  the  pitch  circle  forms 
a part,  will  be  called  the  construction  pitch  circle , as  designated 
on  the  drawing,  Fig.  18,  to  distinguish  it  from  the  actual 
pitch  circle  of  the  gear.  The  same  reasoning  would  hold 


40 


GEAR  CALCULATIONS. 


§17 


for  all  the  other  circles  but  they  are  not  so  marked.  The 
surface  on  which  the  large  ends  of  the  teeth  are  placed  is  a 
cone,  which  if  rolled  out  into  a plane,  that  is  if  the  cone  were 
developed,  the  addendum  circle,  pitch  circle,  base  circle 
working-depth  circle,  and  root  circle  would  roll  out  into  the 
curves  shown  in  Fig.  18. 

Inasmuch  as  it  is  not  practicable  to  construct  cones  and 
lay  out  teeth  on  them,  it  has  become  the  custom  to  lay 
out  the  developed  teeth  on  these  construction  lines.  They 
differ  slightly  from  the  actual  teeth  but  not  enough  to 
necessitate  a different  method  for  their  laying  out. 

To  lay  out  the  curves  for  the  larger  ends,  lay  off  on  the 
construction  pitch  circle  spaces  equal  to  the  circular  pitch. 
The  length  of  these  spaces  is  found  by  dividing  the  circum- 
ference of  the  pitch  circle  of  the  gear  by  the  number  of 
teeth.  Divide  each  space  into  two  parts  to  represent, 
respectively,  the  thickness  of  the  tooth  and  the  width  of  the 
space,  thus  obtaining  the  pitch  points  of  the  teeth.  The  tooth 
curves  are  then  to  be  drawn  through  these  pitch  points. 

75.  Tootb  Curves  by  Odontograph  Table. — When 
the  involute  system  of  teeth  is  used,  the  distance  from  the 
construction  pitch  circle  at  which  to  draw  the  base  circle  is 
to  be  calculated  from  the  diameter  of  the  construction  pitch 
circle.  In  using  the  involute  or  the  cycloidal  odontograph 
table,  the  number  of  teeth  to  be  used  in  selecting  from  the 
table  the  factor  for  calculating  the  face  and  flank  radii,  or 
the  distances  from  the  pitch  circle  to  the  lines  of  face  and 
flank  centers,  is  the  number  found  by  dividing  the  circum- 
ference of  the  construction  pitch  circle  by  the  circular  pitch  ; 
in  other  words,  instead  of  using  the  actual  number  of  teeth 
in  the  gear,  use  the  number  of  teeth  there  would  be  in  a 
gear  having  the  required  pitch  and  a diameter  equal  to  that 
of  the  construction  pitch  circle.  In  dividing  the  circumfer- 
ence of  the  construction  pitch  circle  by  the  circular  pitch, 
the  result  will  rarely  be  a whole  number  and  hence  the  near- 
est whole  number  is  taken. 

To  draw  the  outlines  of  the  inner  ends  of  the  teeth,  a set 
of  arcs  is  drawn  similar  to  those  drawn  for  the  outer  ends, 


GEAR  CALCULATIONS. 


41 


§17 

using  radii  equal  to  the  distances  f'  in,  f n' , f d' , 
and  f n,  or  g'  in' , g'  n,  g'  d' , and  g'  n' , and  laying  out  the 
teeth  on  these  arcs  in  accordance  with  the  general  method 
used  for  the  outer  ends.  It  will  generally  be  better  to  draw 
these  arcs  with  the  same  centers  with  which  the  arcs  for 
the  outer  ends  were  drawn,  as  shown  in  Fig.  18.  Instead  of 
calculating  the  pitch  for  the  inner  ends,  a convenient 
method  of  locating  the  pitch  points  is  to  draw  lines  from  the 
centers  to  the  pitch  points  of  the  outer  ends,  as  shown  by  the 
dotted  lines  f x,  fy , gx',  and  gy'.  The  points  where  these 
lines  intersect  the  construction  pitch  circles  for  the  inner 
ends  of  the  teeth  will  be  the  pitch  points  through  which  to 
draw  the  curves  for  the  outlines  of  the  inner  ends. 


WORM-WHEELS  AND  WORMS. 


KINDS  OF  WORM-WHEELS. 

76.  Description  of  Worm  and  Worm-Wheel. — A 

worm  and  worm-wheel  are  a combination  of  machine  ele- 


ments composed  of  a screw  and 
a gear  that  is  used  for  trans- 
mitting motion  from  one  shaft 
to  another  at  right  angles  to 
each  other  when  the  shafts  are 
not  in  the  same  plane.  It  is 
especially  adapted  to  transmis- 
sion when  it  is  desired  to  change 
small  pressure  at  high  speed  to 
high  pressure  at  low  speed. 
The  worm,  as  a reference  to 
Fig.  19  will  show,  is  simply  a 
screw  whose  threads  fit  the 
teeth  of  the  worm-wheel. 

A worm  is  a screw  with  a 
thread  of  such  a form  that  its 
cross-section  is  the  same  as  thai 


of  a gear-tooth  or  a tooth, 


GEAR  CALCULATIONS. 


42 


§17 


the  worm  being  intended  to  mesh  with  a special  form  of 
spur  gear  called  a worm-wheel. 

A worm-wheel  is  a gear  with  which  a worm  meshes. 
Worm-wheels  may  be  plain  spur  gears  with  their  teeth  cut 
at  an  angle,  or  they  may  be  special  spur  gears  made  to  fit 
the  worm-thread  accurately. 

In  practice,  a worm-wheel  is  made  in  one  of  the  three 
different  ways  shown  in  Fig.  20.  In  (a)  the  teeth  are 


Fig.  20. 


curved  to  fit  the  worm ; such  a wheel  is  cut  with  a hob,  and 
is,  hence,  called  a bobbed  worm-wheel.  The  tool,  or  hob, 
used  for  cutting  this  wheel  is  practically  a duplicate  of  the 
worm,  except  that  the  outside  diameter  of  the  hob  is  slightly 
greater  than  that  of  the  worm,  to  allow  for  clearance.  The 


GEAR  CALCULATIONS. 


43 


worm  will  fit  the  worm-wheel  if  the  cutting  is  carefully 
done,  and  the  contact  between  the  worm  and  worm-wheel 
will  be  all  that  can  be  desired.  A hobbed  worm-wheel 
should  always  be  used  if  much  power  is  to  be  transmitted, 
as  it  will  outlast  either  of  the  gears  shown  in  Fig.  20  ( b ) 
and  (c). 

77.  In  Fig.  20  ( b ),  the  wheel  is  seen  to  have  straight 
teeth  cut  at  an  angle  to  the  axis;  this  angle  is  made  to  suit 
the  angle  of  the  helix  of  the  worm.  Obviously,  the  contact 
of  the  threads  of  the  worm  with  the  teeth  of  such  a wortn- 
wheel  is  rather  imperfect;  since  this  kind  of  a worm-wheel 
can  be  cut  with  an  ordinary  standard  gear-cutter  at  an 
expense  but  slightly  in  excess  of  that  of  a spur  gear,  it  is 
much  used  for  light  work.  The  worm-wheel  with  straight 
teeth  at  an  angle  to  the  axis  is  designed  by  the  same  rules 
as  a spur  gear;  the  angle  that  the  teeth  make  with  the  axis 
is  determined  by  trial  in  cutting  it. 

Fig.  20  ( c ) shows  a form  of  worm-wheel  that  is  occasion- 
ally used  on  gear-cutting  engines  where  a man  has  to  take 
hold  of  the  gear  and  turn  it  by  hand.  One  advantage  these 
teeth  possess  is  that  they  are  so  protected  as  to  be  less  liable 
to  injury  than  those  shown  in  Fig.  20  ( a ) and  ( b ). 

The  outside  diameter  of  a worm-wheel  of  this  kind  may 
be  the  same  as  that  of  the  spur  wheel  having  the  same  pitch 
and  number  of  teeth.  For  ordinary  work,  the  notches  are 
frequently  cut  with  a fly  cutter  set  to  a radius  slightly 
larger  than  that  corresponding  to  the  outside  diameter  of 
the  worm.  If  a standard  cutter  of  the  right  pitch  and 
diameter  is  available,  it  should  be  used  in  preference  to  the 
fly  cutter.  Nothing  is  to  be  gained  by  curving  the  face  of 
the  wheel  to  suit  the  worm  when  a worm-wheel  of  the  kind 
shown  in  Fig.  20  (c)  is  not  to  be  finished  by  hobbing. 
Worm-wheels  of  this  kind  are  frequently  very  carefully  and 
accurately  made  and  used  in  graduating  machines  or  divi- 
ding engines.  Worm-wheels  of  this  kind  may  also  be 
finished  by  hobbing,  but  the  hob  is  not  sunk  into  the  wheel 
to  as  great  a depth  as  in  the  wheel  shown  in  Fig.  20  (a). 


44 


GEAR  CALCULATIONS. 


§ 1? 


WORM-WHEEL  CALCULATIONS. 

78.  Velocity  Ratio  of  Worm-Wheels. — The  num- 
ber of  teeth  that  a worm-wheel  must  have  yto  produce  a 
given  velocity  ratio  is  found  as  follows  : 

Rule. — Multiply  the  number  of  revolutions  that  the  worm 
is  to  make  for  one  revolution  of  the  worm-wheel  by  the  num- 
ber of  threads  of  the  worm. 

Example  1. — If  a single-threaded  worm  is  to  make  56  revolutions  in 
order  to  revolve  the  worm-wheel  once,  how  many  teeth  should  the 
latter  have  ? 

Solution. — Applying  the  rule  just  given,  we  get  56  x 1 ==  56.  Ans. 

Example  2. — If  a triple-threaded  worm  is  to  make  24  revolutions  in 
order  to  revolve  the  worm-wheel  once,  how  many  teeth  should  the 
latter  have  ? 

Solution. — Applying  the  rule,  we  get  24  X 3 = 72.  Ans. 

79.  Worm-Wheel  With  30  or  More  Teeth. — To 

design  a worm-wheel  that  is  to  be  hobbed  and  has  30  or 


more  teeth,  first  of  all  calculate  the  pitch  diameter  a b , 
Fig.  21,  as  follows : 

Rule.  — Multiply  the  number  of  teeth  by  the  distance 
between  centers  of  adjacent  threads  of  the  worm  and  divide 
the  product  by  3.1^16. 

Observe  that  in  the  case  of  a single-threaded  worm,  the 
distance  between  centers  of  adjacent  threads  is  equal  to  the 
amount  the  thread  advances  in  1 revolution,  or  the  lead  of 
the  thread.  In  the  case  of  a multiple-threaded  worm,  the 


17 


GEAR  CALCULATIONS. 


45 


distance  between  centers  of  adjacent  threads  is  the  lead 
divided  by  the  number  of  threads. 

Example. — Calculate  the  pitch  diameter  of  a worm-wheel  having 
42  teeth  for  a double-threaded  worm  having  a lead  of  1 inch. 

Solution. — The  distance  between  centers  of  adjacent  threads  of 
the  worm  is  1 -s-  2 = .5  in.  Applying  the  rule,  we  get 

42  v 5 

Q * ’ m 6.684  in.  Ans. 


80.  Throat  Diameter  of  a Worm-Wheel. — The 

throat  diameter  of  the  worm-wheel,  as  c d,  Fig.  21,  is  calcu- 
lated as  follows : 


Rule. — Divide  twice  the  pitch  diameter  by  the  number  of 
teeth  and  add  the  quotient  to  the  pitch  diameter. 

Example. — Taking  the  example  last  given,  what  should  be  the 
throat  diameter  ? 

Solution. — Applying  the  rule,  we  get 


6.684 


6.684  X 2 
42 


7.002  in.  Ans. 


81.  Depth  of  Tooth  of  a Worm-Wheel. — In  accord- 
ance with  Brown  & Sharpe  practice,  the  depth  c e of  the 
tooth  is  calculated  by  the  following  rule: 

Rule. — Multiply  the  distance  between  centers  of  adjacent 
threads  of  the  worm  by  . 6866. 

Example. — Taking  the  last  example  again,  what  should  be  the  depth 
of  the  teeth  ? 

Solution. — The  distance  between  centers  of  adjacent  threads  of 
the  worm  is  .5  in.  Applying  the  rule  just  given,  we  have 

.5  X .6866  = .8433  in.  Ans. 

The  diameter  of  the  blank  is  most  conveniently  obtained 
by  measuring  a scale  drawing  of  the  worm-wheel.  The 
angle  /may  be  made  from  60°  to  90°. 

82.  Worm-Wheel  With  Less  Than  30  Teeth. 

When  the  worm-wheel  has  less  than  30  teeth,  calculate  the 


46 


GEAR  CALCULATIONS. 


§17 

pitch  diameter  by  the  rule  given  in  Art.  79,  and  the  depth 
of  the  teeth  by  the  rule  given  in  Art.  81  ; the  throat  diam- 
eter is,  however,  to  be  calculated  by  the  following  rule: 

Rule. — Multiply  the  product  of  the  distance  between  cen- 
ters of  adjacent  threads  of  the  worm  and  the  number  of  teeth 
of  the  worm-wheel  by  .298.  Add  to  it  1.273  times  the  dis- 
tance between  centers  of  adjacent  threads  of  the  worm. 

Example. — Find  the  throat  diameter  for  a worm-wheel  with  24  teeth 
meshing  with  a single-threaded  worm  having  a lead  of  .75  inch. 

Solution. — Since  the  worm  is  single-threaded,  the  distance  between 
centers  of  adjacent  threads  is  .75  in.  Applying  the  rule,  we  get 

.75  X 24  X -298  + 1.278  X .75  = 6.319  in.  Ans. 


WORM-CALCULATIONS. 

83.  Pitch  Diameter  of  a Worm. — The  velocity 
ratio  of  a worm  and  worm-wheel  is  independent  of  the 
relative  pitch  diameters  of  the  worm-wheel  and  worm,  from 
which  fact  it  follows  that  in  designing  a worm  and  worm- 
wheel  for  a given  distance  between  centers,  we  have  the 
choice  of  many  different  designs.  One  good  method  of  pro- 
cedure when  the  distance  between  centers  is  given,  is  to 
choose  some  convenient  lead  of  thread  for  the  worm  that 
can  be  cut  readily  in  an  engine  lathe.  The  lead,  or  pitch, 
of  the  worm-thread  divided  by  the  number  of  threads  on 
the  worm  will  give  the  pitch  of  the  teeth  for  the  worm- 
wheel.  From  this,  compute  the  pitch  diameter  of  the 
worm-wheel.  Subtract  half  the  pitch  diameter  of  the  worm- 
wheel  from  the  distance  between  centers  and  double  the 
remainder,  in  order  to  obtain  the  pitch  diameter  of  the 
worm.  If  a comparison  of  the  pitch  diameter  of  the  worm 
with  the  pitch  diameter  of  the  worm-wheel  shows  the  former 
to  be  larger  than  is  considered  desirable,  choose  a coarser 
thread  for  the  worm  and  again  compute  the  pitch  diameters. 
Repeat  this  series  of  operations  until  the  ratio  of  the  two 
pitch  diameters  is  considered  to  be  about  right. 


§17 


GEAR  CALCULATIONS. 


47 


84.  Outside  Diameter  of  Worm. — The  pitch  diam- 
eter a of  the  worm,  as  represented  by  the  lines  be  and  de , 


e 


Fig.  22. 


Fig.  22,  should  always  be  computed  as  stated  in  Art.  83. 
When  the  worm-wheel  has  30  or  more  teeth,  calculate  the 

outside  diameter  as  follows: 

• 

Rule. — Multiply  the  distance  f between  centers  of  adjacent 
threads  of  the  worm  by  .6866  and  add  the  product  to  the 
pitch  diameter  of  the  worm. 

Example. — A triple-threaded  worm  is  to  .have  a pitch  diameter  of 
3 inches  and  a lead  of  thread  of  1.5  inches.  What  should  be  the 
diameter  of  the  blank  for  the  worm  ? 

Solution. — Since  the  worm  is  triple-threaded,  the  distance  between 
centers  of  adjacent  threads  is  1.5  -s-  3 = .5  in.  Applying  the  rule  just 
given,  we  get 

3 + .5  X .63G6  = 3 318  in.  Ans. 

The  total  depth  g'  -\-  h of  the  worm-thread  is  equal  to  the 
depth  of  tooth  of  the  worm-wheel,  and  is,  hence,  to  be  cal- 
culated by  the  rule  given  in  Art.  81. 


48 


GEAR  CALCULATIONS. 


§17 


85.  Worm-Thread. — The  width  i,  Fig.  22,  of  the 
space  between  threads  at  the  top  is  to  be  calculated  as 
follows : 

Rule. — Multiply  the  distance  between  centers  of  adjacent 
threads  by  .665. 

Example. — Taking  the  same  worm  as  in  the  example  in  Art.  84, 
what  should  be  the  width  of  the  thread  at  the  top  ? 

Solution. — Applying  the  rule,  we  get 

.5  X -665  = .333  in.  Ans. 

86.  The  width  j,  Fig.  22,  of  the  bottom  of  the  . space 
between  the  threads  is  to  be  found  as  follows: 

Rule. — Multiply  the  distance  between  centers  of  adjacent 
threads  of  the  worm  by  .SI. 

Example. — Calculate  the  width  of  the  space  between  threads  of  the 
worm  mentioned  in  the  example  given  in  Art.  84. 

Solution. — Applying  the  rule  just  given,  we  get 
.5  X .31  = .155  in.  Ans. 

If  the  dimensions  of  the  space  between  the  threads  are 
calculated  by  the  rules. given  here  and  in  Arts.  8 1 , 85,  and 
86,  the  angle  between  the  sides  of  the  thread  will  be  almost 
exactly  29°,  which  is  the  standard  angle  for  worm-threads 
that  has  been  almost  universally  adopted. 

87.  Worm  for  Worm-Wheel  With  Less  than 
30  Teeth. — The  outside  diameter  of  a worm  intended  for  a 
worm-wheel  having  less  than  30  teeth  and  having  a throat 
diameter  made  in  accordance  with  the  rule  given  in  Art.  82, 
and  a depth  of  tooth  made  in  accordance  with  the  rule  given 
in  Art.  81,  may  be  calculated  as  follows: 

Rule. — Multiply  the  number  of  teeth  of  the  zvorm-wheel 
by  the  distance  between  centers  of  adjacent  threads  of  the 
worm,  and  multiply  the  product  by  . lift.  Subtract  the  last 
product  from  the  distance  between  centers  of  the  worm  and 
worm-wheel , and  multiply  the  remainder  by  2. 


§17  ■ 


GEAR  CALCULATIONS. 


49 


Example. — The  distance  between  centers  of  a worm  and  worm- 
wheel  is  3 inches.  The  worm-wheel  has  24  teeth,  and  the  worm  is 
single-threaded  with  a lead  of  thread  of  .5  inch.  What  should  be  the 
outside  diameter  of.  the  blank  for  the  worm  ? 

Solution. — Applying  the  rule  just  given,  we  get 

2 X (3  - 24  X .5  X .149)  = 2.424  in.  Ans. 

The  outside  diameter  of  the  blank  for  the  worm  having 
been  calculated  by  the  preceding  rule,  the  space  between 
the  threads  of  the  worm  is  to  be  made  according  to  the  rules 
given  in  Arts.  81,  85,  and  86. 


C.  S.  11, -35 


GEAR-CUTTING, 


SYSTEMS  AND  PROCESSES. 


SYSTEMS. 

1.  There  are  two  general  systems  of  forming  gear-teeth 
by  cutting  operations,  which  may  be  called  the  duplication 
and  the  generation  systems. 

2.  In  the  duplication  system,  the  cutting  tool  either 
has  ?l  profile  corresponding  to  the  shape  of  the  space  between 
two  gear-teeth,  or  it  has  a cutting  point,  or  edge,  that  is 
guided  by  a templet.  In  either  case,  the  cutting  tool  merely 
duplicates  a tooth  outline,  but  does  not  generate  one.  From 
this  it  follows  that  under  the  duplication  system  the  correct- 
ness of  the  tooth  curves  depends  primarily  on  the  degree 
of  accuracy  within  which  the  profile  of  the  cutting  tool  or  of 
the  templet  represents  the  true  tooth  curve.  This  consid- 
eration involves  a duplication  of  any  errors  that  may  exist 
in  the  cutter,  or  a reproduction  to  a reduced  scale  of  any 
errors  of  the  templet. 

3.  The  generation  system  will,  in  general,  produce 
more  accurate  tooth  curves  than  the  duplication  system. 
As  implied  by  the  name,  the  tooth  curves  are  generated 
mechanically  for  each  tooth;  in  consequence,  the  errors  are 
very  small. 

§ IB 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


GEAR-CUTTING. 


§18 


METHODS  AND  PROCESSES. 

4.  In  each  system  of  gear-cutting  there  is  a number  of 
different  processes  by  means  of  which  gear-teeth  may  be 
formed;  the  processes  most  commonly  used  are  here  briefly 
explained. 


5.  There  are  two  distinct  and  radically  different  proc- 
esses in  the  duplication  system,  both  of  which  are  used  in 
practice.  Incidentally,  it  may  be  remarked  that  at  present 
the  duplication  system  is  the  one  in  most  general  use.  The 
two  processes  in  that  system  are  called  the  formed-cutter 
process  and  the  templet-planing  process. 


FORMED-CUTTER  PROCESS. 

6.  In  the  formed-cutter  process,  a rotary  cutter 
(a  formed  milling  cutter)  or  a planer  tool  having  a profile 
equal  to  the  space  between  two  teeth  is  used  for  milling  or 
planing  out  the  spaces,  thus  reproducing  its  own  profile 
within  a reasonable  limit  of  variation.  In  this  process,  the 
gear  blank  remains  stationary  while  a space  is  being  cut; 
that  is,  it  does  not  revolve  about  its  axis  during  the  cutting 
operation.  Upon  the  completion  of  each  space,  the  blank  is 
revolved  the  proper  part  of  a revolution,  which  is  measured 
or  obtained  by  the  aid  of  some  suitable  indexing  mechanism. 
On  the  whole,  it  will  be  found  that  the  best  work  can  be 
done  with  a formed  milling  cutter,  which  not  only  will  work 
faster,  but,  also,  by  reason  of  its  numerous  cutting  edges 
and  its  peculiar  formation,  will  preserve  its  profile  much 
longer  than  the  planing  tool  with  its  single  cutting  edge. 

7m  The  formed-cutter  process,  in  which  a formed  milling 
cutter  is  employed,  is  at  present  the  one  in  most  extensive 
use  for  the  cutting  of  spur  gears  and  sprocket  wheels;  it  is 
also  largely  used  for  bevel  gears,  although,  by  reason  of  the 
tooth  profile  changing  in  size  throughout  the  length  of  the 
face  of  a bevel  gear,  the  formed-cutter  process  can,  at  its 
best,  produce  only  an  approximately  correct  bevel  gear. 


GEAR-CUTTING. 


3 


§ 18 


8.  The  use  of  a formed  planing  tool  is  inadvisable  when 
conditions  permit  a formed  milling  cutter  to  be  employed  ; 
the  planing  tool  is  convenient,  however,  for  some  work,  and 
allows  a machine  like  a slotter,  a key  seater,  a shaper,  or  a 
planer  to  be  used  for  work  beyond  the  range  of  a milling 
machine  or  gear-cutting  machine,  and  in  isolated  cases  will 
allow  gears  to  be  cut  when  no  machine  fitted  for  a rotary 
cutter  is  available. 


TEMPLET-PLANING  PROCESS. 

9.  In  the  templet-planing  process,  a round  pointed 
planing  tool  is  guided  by  a properly  shaped  templet  through 
the  intervention  of  suitable  mechanism,  and  copies  the 
profile  given  by  the  templet  either  to  the  same  scale  or  to  a 
reduced  scale.  This  process  is  chiefly  used  for  planing  the 
teeth  of  bevel  gears  and  miter  gears,  and  involves  the  use 
of  a special  machine.  The  teeth  of  spur  gears  and  sprocket 
wheels  can  be  cut  with  the  templet-planing  process,  but  not 
as  fast  as  with  the  formed-cutter  process. 


CONJUGATE-TOOTH  METHOD. 

1 ().  There  is  but  one  method  of  generating  correct  tooth 
curves  that  has  come  into  practical  use.  When  a gear-tooth 
cutter  operates  on  a gear  blank  generating  teeth,  while 
the  cutter  and  blank  roll  together  without  slipping,  then  the 
teeth  formed  on  the  blank  are  conjugate  to  the  teeth  of  the 
cutter.  All  gears  generated  with  the  same  cutter  by  this 
process  are  conjugate  to  the  cutter  and  to  each  other. 
Gears  made  in  this  way  are  generated  by  the  conjugate- 
tooth  method,  and  will  roll  on  each  other  without  slipping, 
that  is,  the  velocity  ratio  is  constant. 

11.  Molding-Planing  Process. — Rotary  cutters  or 
planing  tools  formed  to  the  profile  of  a gear-tooth  having 
the  correct  size  may  be  used  for  generating  conjugate  teeth 


4 


GEAR-CUTTING. 


18 


on  a gear  blank.  In  order  to  form  these  teeth  in  one  process, 
a planing  tool  is  made  in  the  form  of  a gear-wheel,  and  is 
reciprocated  past  the  gear  blank,  to  which  it  is  connected 
in  such  a manner  that  the  cutter  and  blank  will  turn  together 
about  their  axes  as  if  they  were  a gear  and  pinion  meshing 
together.  The  rotation  takes  place  when  the  pinion  acting 
as  a cutter  is  clear  of  the  blank. 

12.  This  process  of  generating  conjugate  teeth  is  tech- 
nically known  as  the  molding-planing  process ; while  it 
is  an  old  and  fairly  well-known  process,  it  has  come  into  prac- 
tical use  but  very  recently.  Its  introduction  is  due  to  the 
Fellows  Gear  Shaper  Company,  of  Springfield,  Vermont,  who 
have  succeeded  in  devising  mechanical  means  of  making  for 
this  purpose  hardened-steel  cutters  with  a degree  of  accu- 
racy so  great  that  the  errors  in  the  tooth  curves  of  the 
cutter  are  practically  insensible.  The  process  is  very  well 
adapted  for  spur  gears,  sprocket  wheels,  and  internal  gears, 
but  has  at  present  not  been  extended  to  screw  gears.  It  is 
claimed  that  not  only  will  the  teeth  be  more  correctly 
formed  by  this  process,  but  that  gears  can  also  be  cut  at  less 
cost  than  by  any  other  process. 

13.  Single-Tooth  Molding-Planing  Process. — 

There  is  one  process  of  forming  conjugate  teeth  by  planing 
in  which  a single-tooth  planing  tool  is  used;  from  this  fact 
it  is  called  the  single-tooth  molding-planing  process. 
It  is  used  in  practice  for  originating  the  tooth  curves  of 
bevel  gears,  and  will  be  explained  in  detail  farther  on. 

14.  Molding-Milling  Process. — A series  of  rotary 
cutters  placed  alongside  each  other  and  having  a longitudi- 
nal section  equal  to  that  of  a rack  of  the  same  pitch  as  the 
gear  to  be  cut,  may  be  used  for  generating  gear-teeth  con- 
jugate to  those  of  the  rack  whose  section  is  represented  by 
the  cutter.  Gears  having  different  numbers  of  teeth  thus 
formed  will  run  together  correctly;  for," since  any  gears 
thus  formed  have  teeth  conjugate  to  the  rack,  it  follows 
that  the  teeth  of  any  two  gears  are  also  conjugate  to  each 
other.  The  cutters  are  given  an  axial  motion  equivalent 


§18 


GEAR-CUTTING. 


5 


to  that  of  a rack,  and  after  passing  clear  around  the 
gear  blank  are  traversed  a little  over  its  face;  the  gear 
blank  is  positively  rotated  just  as  if  it  were  in  mesh  with 
the  generating  rack,  and,  in  consequence,  gear-teeth  conju- 
gate to  those  of  the  rack  are  generated.  This  process  may 
be  called  the  molding-milling  process;  it  has  been  put 
into  practical  use  in  a modified  form  by  Mr.  Ambrose 
Swasey,  of  the  firm  of  Warner  & Swasey,  Cleveland,  Ohio. 

15.  Hobbing  Process. — There  is  one  case  of  genera- 
ting conjugate  teeth  by  a rotary  cutter  that  is  in  general 
use.  This  case  is  the  making  of  accurate  worm-wheels  by 
hobbing;  the  hob  is  a special  form  of  a rotary  cutter,  and 
produces  teeth  conjugate  to  those  of  a worm. 


DUPLICATION  SYSTEM. 


FORMED-CUTTER  PROCESS. 


INTRODUCTION. 

16.  When  a planing  tool  is  to  be  used  for  cutting  gear- 
teeth,  the  exact  tooth  form  of  opposite  sides  of  two  adjacent 
teeth  is  laid  out  on  a piece  of  sheet  metal,  as  sheet  zinc,  and 
a templet  is  then  formed  to  which  the  planing  tool  is  fitted. 

Milling  cutters  for  all  the  standard  diametral  pitches  in 
use  can  be  obtained  from  manufacturers  making  a specialty 
of  this  work.  Such  cutters  are  made  by  the  use  of  special 
machinery,  and  are  so  accurately  and  cheaply  made  that  it 
does  not  pay  any  one,  as  a general  rule,  to  make  them 
himself. 


STANDARD  CUTTERS. 

17.  While,  correctly  speaking,  there  should  be  a differ- 
ently shaped  cutter  for  every  number  of  teeth  in  a gear  of 
the  same  pitch,  it  lias  been  shown  practically  that  the 


GEAR-CUTTING. 


0 


§ IB 


TABLE  OF  STANDARD  CUTTERS. 


Epicycloidal. 

Involute. 

Pratt  & Whitney. 

Brown  & Sharpe. 

Designating  Mark  of 
Cutter. 

Number  of  Teeth 
of  Gear. 

Designating 
Mark  of  Cutter. 

Number  of 
Teeth 
of  Gear. 

Designating 
Mark  of  Cutter. 

Number  of 
Teeth 
of  Gear. 

1 

12 

A 

12 

1 

135  to  rack 

2- 

13 

B 

13 

2 

55-134 

o 

O 

14 

C 

14 

3 

35-54 

4 

15 

D 

15 

4 

26-34 

5 

16 

E 

16 

5 

21-25 

6 

17 

F 

17 

6 

17-20 

7 

18 

G 

18 

7 

14-16 

8 

19 

H 

19  . 

8 

12-13 

9 

20 

I 

20 

10 

21-22 

J 

21-22 

11 

23-24 

K 

23-24 

12 

25-26 

L 

25-26 

13 

27-29 

M 

27-29 

14 

30-33 

N 

30-33 

15 

34-37 

O 

34-37 

16 

38-42 

P 

38-42 

17 

43-49 

Q 

43-49 

18 

50-59 

R 

50-59 

19 

60-75 

S 

60-74 

20 

76-99 

T 

75-99 

21 

100-149 

U 

100-149 

22 

150-299 

V 

150-249 

23 

300  and  over 

w 

250  and  over 

24 

Rack 

X 

Rack 

GEAR-CUTTING. 


7 


§ 18 

divergence  of  the  tooth  curves  is  so  gradual  that  one  cutter 
may  be  made  to  answer  for  several  numbers  of  teeth  with- 
out introducing  any  serious  error. 

In  the  cycloidal  system  of  gearing  there  are  24  cutters  in 
a set  for  each  diametral  pitch.  Incidentally,  it  may  be  re- 
marked that  the  cycloidal  system  is  commonly  miscalled  the 
epicycloidal  system  ; in  fact,  all  manufacturers  stamp  cutters 
intended  for  the  cycloidal-tooth  form  “ Epicycloidal,”  and 
refer  to  them  by  that  name.  In  the  involute  system  of  gear- 
ing there  are  8 cutters  in  a set.  A set  of  cutters  comprises 
all  the  cutters  required  for  gears  above  12  teeth  up  to  and 
including  the  rack,  and  will  cut  gears  that  are  interchange- 
able. The  different  cutters  of  each  set  are  designated  by 
the  different  makers  by  letters  or  figures;  the  accompanying 
Table  of  Standard  Cutters  gives  the  designating  marks  and 
the  number  of  teeth  of  the  gear  for  which  the  cutter  can  be 
used.  For  instance,  by  referring  to  the  table  it  is  seen  that 
a number  21  Pratt  & Whitney  epicycloidal  cutter  is  intended 
for  gears  having  from  100  to  149  teeth,  inclusive  of  both 
numbers,  and  a Brown  & Sharpe  epicycloidal  cutter  desig- 
nated by  the  letter  S is  intended  for  gears  having  from 
60  to  74  teeth,  inclusive  of  both.  Likewise,  a number  2 
involute  cutter  is  intended  for  gears  having  between  55 
and  134  teeth,  inclusive  of  both. 


STANDARD  DITCHES. 

1 8.  The  standard  diametral  pitches  that  Pratt  & Whit- 
ney make  epicycloidal  cutters  for  are  as  follows:  1£,  2,  2^, 

3,  31,  4,  5,  6,  7,  8,  9,  10. 

The  standard  diametral  pitches  that  Brown  & Sharpe 
make  epicycloidal  cutters  for  are  as  follows:  3,  4,  5,  6, 
8,  10. 

On  a special  order,  Brown  & Sharpe  furnish  the  following 
pitches  for  epicycloidal  cutters:  2,  2J,  2£,  2f,  3J,  7,  9,  12, 

14,  16. 

Involute  cutters  can  be  obtained  on  regular  order  for  the 


GEAR-CUTTING. 


8 


§18 


following  diametral  pitches:  3,  4,  5,  6,  7,  8,  9,  10,  11,  12, 

14,  16,  18,  20,  22,  24,  26,  28,  30,  32,  36,  40,  48. 

On  special  order,  Brown  & Sharpe  will  furnish  involute 
cutters  for  the  following  diametral  pitches:  2,  2£,  2£, 
2f,  3£,  3£,  3f,  4£,  5^,  13,  15,  38,  44,  50,  56,  60,  64,  70, 
80,  120. 

. Cutters  for  other  pitches  can  usually  be  furnished  by  manu 
facturers  to  order,  but  naturally  only  at  an  advance  in  price. 
Neither  epicycloidal  nor  involute  cutters  are  regularly  in  the. 
market  for  gears  designed  on  the  circular-pitch  system ; such 
cutters  can  be  obtained  only  on  special  order  at  a propor- 
tionate advance  in  price. 


DEPTH  OF  CUT. 

19.  Calculating  the  Depth. — The  correct  depth  of 
cut  for  standard  epicycloidal  and  involute  cutters  made 
according  to  the  Brown  & Sharpe  system  is  calculated  as 
follows: 

Rule. — Divide  2.157  by  the  diametral  pitch. 

Example. — Find  the  proper  depth  of  cut  for  a 2-pitch  Brown  & 
Sharpe  cutter. 

Solution. — Applying  the  rule  just  given,  we  get 

2.157  . n-ro  • i a 

— - — = 1.078  m.,  nearly.  Ans. 

20.  For  epicycloidal  cutters  made  by  Pratt  & Whitney, 
the  correct  depth  of  cut  is  obtained  as  follows: 

Rule. — Divide  2.125  by  the  diametral  pitch. 

Example. — Find  the  depth  of  cut  of  a standard  6-pitch  Pratt  & 
Whitney  epicycloidal  cutter. 

Solution. — Applying  the  rule  just  given,  we  have 

2.125  oe?.  . , 

— - — = .354  in.,  nearly.  Ans. 

21.  Setting  Cutter  for  Depth. — The  cutter  may  be 
set  to  the  correct  depth  by  observing  the  indication  of  the 


GEAR-CUTTING. 


9 


§18 

graduated  dials  on  the  feed-screws.  If  the  gear  blank  has 
been  turned  to  the  correct  size,  the  cutter  is  first  set  to  touch 
the  blank;  it  is  then  run  clear  of  the  blank  and  the  axes  of 
the  cutter  and  blank  are  brought  together  an  amount  equal 
to  the  calculated  depth  of  cut.  When  the  gear  blank  is 
under  size,  one-half  of  the  difference  between  the  true  diam- 
eter and  the  actual  diameter  should  be  subtracted  from 
the  calculated  depth  of  cut;  the  remainder  will  be  the  depth 
to  which  the  cutter  is  to  be  set.  If  the  gear  blank  is  over 
size,  it  should  be  turned  down. 

22.  Gear-Tootli-Deptti  Gauge. — When  the  blank 
has  been  turned  to  the  correct  size , a gear-tooth-depth 
gauge  may  be  used  for  mark- 
ing the  correct  depth  of  cut  on 
the  blank.  Such  a gauge  is 
shown  in  Fig.  1.  It  has  at 
one  end  a rectangular  slot,  the 
width  of  which  is  made  equal 
to  the  depth  of  cut  for  the 
diametral  pitch  the  gauge  is 
intended  for.  The  point  a is 
hardened  and  is  used  for  scri- 
bing a line  representing  the  cor- 
rect depth  of  tooth  on  the 
blank,  by  applying  the  gauge 
as  shown  in  the  illustration 
and  observing  the  precaution 
of  holding  it  radially  during 
the  scribing.  The  cutter  is  then  sunk  into  the  blank  to 
the  depth  indicated  by  the  scribed  line. 


GANG  CUTTERS. 

23.  Two  or  more  specially  shaped  cutters  may  be  placed 
alongside  each  other  at  a distance  equal  to  the  pitch,  and 
may  be  used  for  cutting  the  teeth  in  the  same  manner  as 


10 


GEAR-CUTTING. 


ordinary  single  cutters.  When  several  cutters  are  thus 
placed,  they  are  called  gang  cutters.  They  may  be  di- 
vided into  two  classes,  which  are:  ( a ) Gang  cutters  that 

finish  teeth  to  an  approximate  shape;  ( b ) gang  cutters  that 
finish  teeth  to  exact  shape. 

24.  The  Clougli  duplex  cutter  belongs  to  the  first 

class,  since  one  gang  of  two  cutters  made  as  shown  in 
Fig.  2 (a)  is  used  for  all  gears  of  the  same  pitch.  For  gears 
of  more  than  30  teeth,  the  teeth  are  finished  entirely  by  the 
inside  faces  of  the  cutters,  as  shown  in  Fig.  2 ( b ) at  a\  gears 
having  a smaller  number  of  teeth  have  the  flanks  of  the  teeth 
finished  by  the  outside  faces  of  the  cutters,  and  the  faces  of 


the  teeth  by  the  inside  faces  of  the  cutters,  as  shown  at  b in 
the  same  figure.  Gears  cut  with  these  cutters  will  have 
approximately  involute  teeth,  and  different  gears  cut  by  the 
same  cutter  will  run  together  fairly  well.  Their  motion 
obviously  cannot  be  as  exact  as  that  of  wheels  cut  by  a cor- 
rect single  cutter.  These  duplex  cutters  are  laid  out  in  such 
a manner  that  the  wheels  cut  by  them  will  mesh  and  run 
with  gears  cut  with  regular  involute  standard  cutters. 


Fig.  2. 


GEAR-CUTTING. 


11 


§ 18 

25.  The  Gould  & Eberliardt  gang  cutter  is  an  ex- 
ample of  a cutter  belonging  to  the  second  class.  If  the  teeth 
of  a gear-wheel  be  examined,  it  will 
be  found  that  usually  several  of  them 
can  be  cut  at  once  if  the  cutter  is 
shaped  to  conform  to  the  tooth  out- 
lines. Thus,  in  Fig.  3,  the  cutter  a 
conforms  to  the  space  a ; the  cutter  b 
conforms  to  the  space  b\  and  as  its 
central  plane  perpendicular  to  its 
axis  of  rotation  passes  through  the 
axis  of  the  gear,  it  is  a standard  cut- 
ter. Finally,  the  cutter  c conforms 
to  the  space  c’.  By  employing  three 
gang  cutters  thus  formed,  three  teeth 
can  be  cut  at  a time,  and,  hence,  the 
indexing  would  be  done  for  three  teeth  instead  of  one.  In 
consequence  of  this,  a gear  can  be  cut  in  less  time  than  is 
required  for  cutting  it  with  a single  cutter,  but  owing  to  the 
increased  heating  it  cannot  be  cut  in  one-third  of  the  time. 
Since  such  gang  cutters  can  have  the  correct  shape  for  only 
one  size  of  a gear,  it  follows  that  a separate  gang  is  required 
for  each  size. 

The  Gould  & Eberhardt  gang  cutter  is  intended  primarily 
for  manufacturing — that  is,  making  a large  number  of  equal 
gears — and  in  its  special  field  is  obviously  far  ahead  of  the 
ordinary  single  cutter.  The  large  number  of  gangs  required 
to  cover  the  whole  range  of  gears  of  each  pitch  makes  it 
rather  unsuitable  for  jobbing  work. 


Z 

MACHINERY  ANI)  ATTACHMENTS. 

26.  In  the  formed-cutter  process,  where  a milling  cut- 
ter is  used,  the  gear  may  be  cut  either  in  a plain  milling 
machine  fitted  with  a suitable  indexing  attachment,  or  in  a 
universal  milling  machine,  or  in  a regular  gear-cutting 
engine. 


12 


GEAR-CUTTING. 


§ 18 

27.  Gear-C  utting  Attachment. — The  simplest  form 
of  gear-cutting  attachment  does  not  differ  in  principle  from 
that  of  the  plain  index  centers,  except  that  the  index  plate 
has  only  one  row  of  holes  and  thus  a rather  limited  range  of 
usefulness.  Other  attachments  have  a large  index  plate 
and  a number  of  different  rows  of  holes  so  as  to  extend  their 
range  of  usefulness.  Sometimes  a still  more  elaborate 
device,  like  that  shown  in  Fig.  4,  is  employed.  In  this  the 
gear  blank  is  mounted  on  a mandrel  and  placed  between  the 
centers  a and  or  it  may  be  mounted  upon  an  arbor  placed 
in  the  spindle  in  place  of  the  center  a.  Inside  of  the  guard  c 


so  arranged  that  the  worm  upon  the  shaft  can  be  disengaged 
from  the  worm-wheel  in  the  case  cy  the  worm-wheel  rotated  by 
hand,  and  a plain  index  pin  used  in  the  holes  in  the  back  of  the 
plate.  The  attachment  shown  can  ordinarily  be  used  only  for 
spur  gears  and  sprocket  wheels;  when  fitted  to  a universal 
milling  machine,  it  can  also  be  used  for  gashing  worm-wheels. 

28.  When  a universal  milling  machine  is  available,  spur 
gears,  worm-gears,  sprocket  wheels,  screw  gears,  and  bevel 
gears  can  be  cut;  but  bevel  gears  can  be  cut  only  approxi- 
mately correct. 

29.  Gear-Cutting  Engine.  — A regular  spur  gear- 
cutting engine  is  only  a special  form  of  a milling  machine, 


Fig.  4. 


§18 


GEAR-CUTTING. 


13 


and  differs  from  it  chiefly  in  that,  as  a general  rule,  the 
indexing  and  also  the  running  back  of  the  cutter  is  done 
automatically. 

Fig.  5 shows  one  form  of  an  automatic  spur  gear-cutting 
engine  built  by  Gould  & Eberhardt,  Newark,  New  Jersey. 
The  gear  blank  is  fastened  in  some  suitable  manner  to  the 
spindle  a;  generally,  an  arbor  is  used,  which,  in  the  de- 
sign shown,  is  supported  at  its  outer  end  by  the  adjustable 


outboard  bearing  b.  Upon  the  spindle  is  fastened  a worm- 
wheel  that  is  enclosed  in  a guard  c in  order  to  protect  it; 
a worm  meshes  with  the  worm-wheel  and  is  in  turn  oper- 
ated by  change  gears  that  revolve  it  a definite  part  of  a 
revolution  each  time  the  cutter  is  clear  of  the  gear  blank 
and  before  it  begins  to  cut.  The  cutter  is  carried  in  a 


14 


GEAR-CUTTING. 


§ 18 


slide  d that  is  moved  parallel  to  the  axis  of  the  spindle  a, 
and  is  fed  automatically  to  the  work  and  returned.  The 
cutter  is  adjusted  for  depth  by  lowering  the  gear  blank. 
A limited  side  adjustment  is  usually  provided  for  the  cutter 
to  allow  cutters  of  different  thicknesses  to  be  set  central. 


30.  A utomatic  gear-cutting  engines  are  often  arranged 
so  that  they  can  be  used  for  cutting  approximately  correct 
bevel  gears.  The  slide  that  carries  the  cutter  is  then  ar- 
ranged in  such  a manner  that  it  can  be  set  at  the  required 
angle  to  the  axis  of  the  spindle. 

31.  Change  Gearing. — The  gearing  that  revolves  the 
shaft  carrying  the  worm  is,  as  a general  rule,  actuated  by  a 
so-called  stop-sliaft,  which  is  provided  with  a suitable 
clutching  mechanism  operated  by  the  cutter  slide.  This 
clutching  mechanism  is  so  arranged  that  it  allows  the  stop- 
shaft  to  make  exactly  one  revolution  whenever  the  return- 
ing cutter  slide  unlocks  it.  The  change  gears  that  will 
produce  a certain  number  of  divisions  are  selected  in  ac- 

. . , . . teeth  in  worm-wheel  T r 

cordance  with  the  ratio  : . In  case  ot 

teeth  to  be  cut 

simple  gearing,  this  is  the  simple  ratio  that  gears  are  to  be 
selected  for;  in  case  of  compound  gearing,  it  is  the  com- 
pound ratio,  which  is  resolved  into  factors.  The  gears  are 
selected  in  the  same  manner  as  is  done  in  gearing  a lathe 
for  thread  cutting  or  a milling  machine  for  the  cutting  of 
helixes. 

In  adjusting  the  gear-cutting  engine,  the  tripping  ar- 
rangement for  the  stop-shaft  clutching  mechanism  must  be 
set  so  that  it  will  act  only  after  the  cutter  on  its  return 
stroke  is  entirely  clear  of  the  gear. 


CUTTING  BEVEL  GEARS  WITH  FORMED  CUTTERS. 

32.  Selecting  the  Cutter. — While  bevel  gears  cut 
with  a cutter  of  fixed  curve  can  be  only  approximately  cor- 
rect, the  comparative  cheapness  of  this  method  has  led  to  its 
being  largely  used.  The  ordinary  cutters  made  for  spur 


GEAR-CUTTING. 


15 


§18 

wheels  should  never  be  used  for  this  purpose,  as  they  will 
cut  the  teeth  of  the  bevel  gear  entirely  too  thin  at  the 
small  end.  Special  miter-gear  and  bevel-gear  cutters  are 
made  for  this  purpose;  these  cutters  are  of  the  involute 
form,  but  thinner  than  the  standard  cutters.  They  are 
numbered  from  1 to  8,  and  cover  the  same  range  as  the 
standard  involute  cutters.  A bevel-gear  cutter  cannot  be 
selected  in  the  same  manner  as  the  ordinary  spur-gear  cut- 
ter, that  is,  directly  in  accordance  with  the  number  of 
teeth  of  the  bevel  gear.  It  is  to  be  selected,  instead,  for  a 
number  of  teeth  that  is  calculated  by  one  of  the  rules  given 
below,  the  first  of  which  is  as  follows: 

Rule. — To  find  the  number  of  teeth  a bevel-gear  cutter  is 
to  be  selected  for , divide  the  number  of  teeth  of  the  bevel  gear 
by  the  natural  cosine  of  the  center  angle  a d e,  Fig.  6. 

Example.  — The  center  angle  of  a bevel  gear  having  24  teeth 
is  53°  15'.  What  number  of  teeth  should  the  cutter  be  selected  for  ? 

Solution. — The  cosine  of  53°  15'  is  .59832.  Applying  the  rule, 
24 

we  get.  e-oqoo  — teeth.  Referring  to  the  Table  of  Standard  Cutters, 

we  find  that  for  gears  having  between  35  and  54  teeth,  a No.  3 cutter 
is  to  be  used.  Hence,  use  a No.  3 bevel-gear  cutter.  Ans. 

33.  When  a drawing  of  the  bevel  gear  is  available,  use 
the  following  rule: 

Rule. — Measure  the  slant  height  of  the  back  cone , as  a b 
in  Fig.  6;  double  it  and  multiply  by  the  diametral  pitch. 
The  product  will  be  the  number  of  teeth  the  cutter  is  to  be 
selected  for. 

Example. — The  slant  height  of  the  back  cone  being  5 inches,  and 
the  diametral  pitch  being  4,  what  number  of  bevel-gear  cutter  is 
to  be  used  ? 

Solution. — Applying  the  rule  just  given,  we  get  5 X 2 X 4 = 40 
teeth.  Referring  to  the  Table  of  Standard  Cutters,  it  is  seen  that 
a No.  3 bevel-gear  cutter  is  to  be  used.  Ans. 

34.  Setting  the  Machine. — The  cutter  having  been 
selected,  place  it  on  its  arbor;  put  the  gear  blank  into  the 


C.  S.  II.— 36 


16 


GEAR-CUTTING. 


§ 18 


machine,  and  set  the  latter  to  the  cutting  angle.  Now, 
set  the  cutter  central  in  respect  to  the  gear  blank;  then 

set  it  to  the  cor- 
rect depth  of  cut, 
measuring  at  the 
large  end  of  the 
blank,  and  cut  two 
adjacent  tooth 
spaces,  as  b and  c 
in  Fig.  7,  which 
leaves  the  tooth  a 
rather  too  thick. 
Set  the  cutter  off 
center  an  amount 
equal  fo  about  TV 
the  thickness  of 
the  tooth  a at  the 
large  end.  Now, 
revolve  the  gear 
blank  toward  the 
cutter  until  the 
latter  will  enter 
one  of  the  central 
cuts  b or  c at  the  small  end  of  the  gear  and  cut  the  one 
side  of  the  tooth  a.  Next, 
set  the  cutter  off  center 
to  the  other  side  of  the 
center  by  the  same 
amount  and  roll  the 
blank  toward  the  cutter 
again  until  it  enters  the 
other  central  slot  at  the 
small  end.  Take  the  cut, 
and  measure  the  thick- 
ness of  the  tooth  a at  the 
pitch  line  at  the  large 
end.  If  its  thickness  is 
more  than  the  quotient 


GEAR-CUTTING. 


17 


§ 18 

obtained  by  dividing  the  circumference  of  the  pitch  circle 
by  twice  the  number  of  teeth,  it  shows  that  the  cutter  must 
be  set  farther  off  center.  This  having  been  done,  the  blank 
is  rolled  toward  the  cutter  and  both  sides  of  the  tooth  a are 
cut  again,  and  the  cycle  of  operations  is  repeated  until  the 
tooth  is  of  the  correct  thickness  at  the  large  end.  The 
gear  blank  can  now  be  cut,  first  setting  the  cutter  off  center 
one  way  the  amount  determined  by  trial  and  cutting  all 
around  the  gear,  and  then  setting  it  off  center  the  other 
way  and  going  around  once  more. 

35.  The  method  given  in  Arts.  32,  33,  and  34  will 
answer  fairly  well  for  teeth  that  are  shorter  than  -J  the  slant 
height  of  the  pitch  cone;  it  will  leave  the  teeth  correct  at  the 
large  end,  but  not  rounding  enough  at  the  small  end.  The 
teeth  must  consequently  be  dressed  with  a file. 

36.  Gear-Tooth  Caliper. — A good  form  of  a caliper 
for  measuring  the  thickness  of  the  gear-teeth  is  shown  in 
Fig.  8.  The  vertical  slide  a is  first  set  until  the  reading  of 


its  vernier  is  equal  to  the  calculated  addendum  of  the  tooth; 
the  caliper  is  then  applied  to  the  gear  with  the  slide  a resting 
on  top  of  a gear-tooth,  as  shown,  and  the  horizontal  jaw  b is 


GEAR-CUTTING. 


18 


§ IB 


brought  against  the  tooth.  The  thickness  of  the  tooth  is 
read  on  the  horizontal  vernier. 


37.  General  Instructions. — When  miter  gears  are 
cut,  both  gears  of  a pair  are  cut  with  the  same  cutter;  when 
bevel  gears  are  cut,  the  proper  number  of  the  cutter  should 
be  computed  for  each  by  the  rules  previously  given.  If  the 
cutting  is  done  in  a machine  where  the  angle  between  the 
axis  of  the  index-head  spindle  and  the  axis  of  the  cutter 
spindle  can  be  changed,  the  angle  should  be  made  90°  before 
beginning  to  set  the  machine.  This  gear-tooth  caliper  does 
not  give  good  results  when  applied  to  the  teeth  of  small 
pinions  unless  care  is  taken  to  see  that  the  points  of  the 
jaws  are  in  contact  with  the  pitch  points  of  the  teeth.  This 
may  necessitate  the  setting  of  the  vertical  scale  to  a greater 
distance  than  the  addendum. 


RACK  CUTTING. 

38.  A rack  may  be  cut  either  with  a planing  tool  or  a 
milling  cutter  shaped  to  conform  to  the  rack  teeth.  The 
pitch  of  the  rack  is  equal  to  the  pitch  of  the  spur  gear  mesh- 
ing with  it,  and  since  cut  spur  gears  are  made  almost  en- 
tirely to  the  diametral-pitch  system,  the  circular  pitch  must 
usually  be  computed  from  it  to  obtain  the  spacing. 

39.  Short  racks  can  readily  be  cut  in  the  horizontal 
milling  machine,  using  the  cross-feed  screw  to  obtain  the 
spacing  and  the  regular  longitudinal-feed  screw  for  feeding. 
The  rack  blank  may  either  be  clamped  to  the  table  or  be 
held  in  the  vise  or  in  a special  fixture. 

40.  Racks  that  are  too  long  to  be  cut  in  this  manner 
can  be  cut  by  means  of  a special  rack-cutting  attachment, 
one  form  of  which  is  shown  in  Fig.  9.  The  cutter  a is 
placed  at  right  angles  to  its  normal  position;  this  allows 
the  feed-screw  b to  be  used  for  spacing  the  teeth  and  the 
cross-feed  screw  for  feeding.  A graduated  dial  c reading 
to  .001  inch  is  placed  on  the  feed-screw,  and  the  correct 


GEAR-CUTTING. 


19 


§ 18 


spacing  is  obtained  by  means  of  it.  The  rack  may  be  placed 
in  a fixture  d made  as  shown,  which  will  take  several  racks 
at  one  time. 

41.  When  racks  are  cut  in  the  milling  machine,  it  is 
strongly  recommended  that  the  gibs  of  the  part  that  is 
moved  in  order  to  obtain  the  spacing  be  set  up  more  firmly 
than  usual  in  order  to  create  enough  friction  to  prevent  any 
shifting,  which  is  liable  to  occur  by  reason  of  the  backlash 
of  the  feed-screw. 


Fig.  9. 


Racks  are  often  cut  in  milling  machines  of  the  planer 
type;  in  that  case,  the  spacing  is  obtained  by  means  of  the 
feed-screw  in  the  cross-rail.  The  head  should  then  have  its 
gibs  set  up  rather  firmly.  The  rack  is  placed  square  across 
the  platen. 

A planing  tool  formed  to  the  correct  shape  may  be 
used  in  a planer,  shaper,  or  slotter,  obtaining  the  spa- 
cing by  means  of  whatever  feed-screw  can  be  used  for  the 
purpose. 


20 


GEAR-CUTTING. 


§18 


TEMPLET-PLANING  PROCESS. 

42.  The  Machine. — The  principle  of  operation  of  a 
templet-planing  machine  intended  for  planing  the  teeth  of 
bevel  gears  is  shown  in  diagrammatic  form  in  Fig.  10. 
The  gear  blank  a is  attached  to  the  index  spindle  b , which 
carries  an  indexing  wheel  c at  its  other  end.  An  arm  d 
supports  a longitudinally  movable  slide  e which  carries  the 
pointed  cutting  tool  f.  The  arm  d is  mounted  on  a univer- 
sal joint  in  such  a manner  that  its  center  of  rotation  g coin- 
cides with  the  axis  of  rotation  of  the  gear  blank.  The 


cutting  tool  is  adjusted  in  the  slide  e in  such  a manner  that 
the  line  of  motion  of  its  cutting  point  passes  exactly  through 
the  center  of  rotation  of  the  arm.  A pin  h is  fastened  to 
the  free  end  of  the  arm,  and  is  in  contact  with  a templet  iy 
which  is  shaped  to  conform  to  a correct  tooth  curve  for  the 
number  of  teeth  contained  in  the  bevel  gear. 


GEAR-CUTTING. 


21 


§ 18 

The  arm  d remains  stationary  while  the  cutting  tool  is 
traversed  through  the  gear  blank.  One  side  of  a tooth  is 
finished  at  a time  by  successive  cuts  converging  toward  the 
apex  of  the  pitch  cone,  which  point,  by  reason  of  the  con- 
struction of  the  machine,  is  also  the  center  of  rotation  g of 
the  arm.  After  the  tool  /"has  cleared  the  blank  on  its  re- 
turn stroke,  the  arm  is  moved  slightly  along  the  templet  i, 
keeping  the  pin  h in  contact  with  the  templet ; the  position 
of  the  arm  and,  hence,  the  formation  of  the  tooth  curves,  is 
thus  determined  by  the  templet.  The  form  of  the  templet 
is  reproduced  on  a smaller  scale  by  the  planing  tool  on  the 
tooth  operated  on,  and  any  errors  existing  in  the  templet 
are  reduced. 

43.  It  is  obvious  that  a different  templet  will  be  re- 
quired for  each  number  of  teeth,  at  least  theoretically. 
Owing  to  the  small  divergence  in  the  shape  of  the  tooth 
curves,  one  templet  can  be  made  to  serve  for  several  gears, 
however,  just  as  is  done  with  formed  gear-cutters.  One 
templet  will  answer  for  all  pitches  within  the  range  of  the 
machine;  different  sizes  of  bevel  gears  are  cut  by  varying 
the  distance  from  the  gear  to  the  center  of  rotation  of 
the  arm  d.  In  an  actual  machine,  the  templet  is  movably 
mounted  on  a quadrant  having  its  center  of  curvature  at^; 
this  adapts  the  machine  for  different  gears,  since  it  allows 
the  angle  between  the  axis  of  the  spindle  and  the  line  of 
motion  of  the  tool  to  be  changed  to  suit  the  number  of  teeth 
of  the  gear. 

44.  Templet-Grinding  Process. — A modification  of 
the  templet-planing  process  has  recently  been  perfected  by 
the  Leland  & Faulconer  Company,  Detroit,  Michigan,  who 
have  substituted  a corundum  wheel  for  the  planing  tool  and 
thus  are  enabled  to  finish  the  teeth  of  hardened-steel  bevel 
gears  to  a correct  shape.  The  fundamental  principle  under- 
lying this  templet-grinding  process  does  not  differ  in  any 
essential  particular  from  that  explained  in  connection  with 
Fig.  10. 


22 


GEAR-CUTTING. 


§ IB 


GENERATION  SYSTEM. 


CONJUGATE-TOOTH  METHOD. 


MOLDING  PROCESS. 

45.  The  different  processes  employed  in  the  conjugate- 
tooth  method  of  generating  gear-teeth  are  all  based  on  the 
so-called  molding  process,  which  has  not  been  put  into 
practical  use,  however,  at  least  not  to  any  extent.  This 
process  may  be  explained  as  follows:  Let  a correctly  formed 
rack  made  of  some  hard  material,  as  steel,  be  passed  over  a 
gear  blank  made  of  a plastic  material,  as  beeswax,  while  the 
blank  is  given  a positive  rotation  that  imparts  to  it  at  the 
pitch  circle  a velocity  equal  to  that  of  the  rack.  Then,  the 
pitch  line  of  the  rack  and  the  pitch  circle  of  the  blank  being 
tangent,  the  teeth  of  the  rack  will  mold  teeth  in  the  blank 
that  are  conjugate  to  its  own. 


MOLDING-PLANING  PROCESS. 

46.  Principle  of  Operation. — Since  the  materials  of 
which  gear-wheels  are  constructed  are  not  plastic,  the  mold- 
ing process  cannot  be  employed  very  readily,  but  the  same 
effect  can  be  produced  by  transforming  the  generating  rack 
into  a cutting  tool  that  reciprocates  across  the  blank  in  the 
direction  of  the  axis  of  the  latter.  The  cutting  tool  does 
not  advance  during  its  cutting  stroke  in  a line  tangent  to 
the  pitch  circle  of  the  blank  and  at  right  angles  to  the  axis 
of  the  latter;  but,  after  the  tool  has  cleared  the  blank  on  its 
return  stroke,  the  tool  and  the  gear  blank  are  given  a slight 
motion  equivalent  to  that  of  a meshing  rack  and  pinion  and 
the  tool  is  reciprocated  through  the  blank  again.  This  cycle 
of  operations  is  repeated  until  the  gear  blank  has  been  trans- 
formed into  a gear.  The  molding  process  thus  becomes  the 


GEAR-CUTTING. 


23 


§18 

molding-planing  process;  in  execution,  however,  this  proc- 
ess is  modified  for  practical  reasons,  the  chief  of  which 
are  the  great  length  of  rack  required  and  the  difficulty  of 
making  it. 

47.  Fellows  Gear-Shaper. — In  the  Fellows  gear- 
shaper,  in  which  machine  the  molding-planing  process  is 
employed,  the  cutter  a , Fig.  11,  is  made  in  the  form  of  a 
gear.  The  process  by  which  the  cutter  is  generated  is 
equivalent  to  its  generation  by  an  involute  rack,  and  it  is 


given  teeth  conjugate  to  those  of  the  generating  rack.  In 
consequence  of  the  method  by  which  the  cutter  is  formed, 
the  teeth  of  all  gears  cut  by  it  are  conjugate  to  the  rack  and 
hence  to  one  another;  that  is,  the  different  gears  will  run 
together  correctly. 


24 


GEAR-CUTTING. 


§ 18 

In  use,  the  cutter  a is  drawn  axially  across  the  face  of  the 
blank  b and  cuts  grooves  corresponding  to  the  shape  of  its 
teeth.  In  beginning  to  cut  a gear,  the  blank  and  cutter  do 
not  revolve,  but  the  center-to-center  distance  between  the 
cutter  and  the  gear  blank  is  shortened  after  each  return 
stroke  of  the  cutter  until  the  correct  depth  of  cut  is  reached. 
The  cutter  and  the  gear  blank  are  then  rotated  a little  by 
positive  means  after  each  return  stroke  in  the  direction 
shown  by  the  arrows;  their  relative  rotations  are  exactly 
the  same  as  if  two  gears  equal  in  size  to  the  cutter  and  gear 
to  be  cut  were  rolling  together.  Conjugate  teeth  are  thus 
generated,  and  one  cutter  will  cut  all  gears  from  a pinion 
to  a rack. 

48.  The  machine  used  is  shown  in  Fig.  12.  The  cut- 
ter a is  carried  on  the  end  of  a ram  that  is  free  to  slide  in  a 
vertical  direction  and  can  be  rotated  about  the  cutter  axis. 
This  ram  is  carried  in  a head  bf  which  is  gibbed  to  ways 
formed  on  the  frame  and  is  movable  horizontally  to  suit 
different  diameters  of  gears  and  different  depths  of  cut. 
The  gear  blanks  c , c are  mounted  on  a vertical  spindle  par- 
allel to  the  line  of  motion  of  the  ram.  The  lower  end  of 
the  spindle  that  receives  the  blank  carries  a worm-wheel 
enclosed  in  the  guard  d\  a worm  meshes  with  this  wheel 
and  in  turn  is  connected  to  change  gearing  that  connects 
the  ram  and  the  spindle  by  a suitable  mechanism  and  forces 
them  to  rotate  together.  Different  velocity  ratios  are  ob- 
tained by  changing  the  change  gears.  The  ram,  sliding 
axially  in  its  bearings,  is  reciprocated  across  the  face  of  the 
blank.  The  gear  blank  is  supported  against  the  cut  by  an 
adjustable  jack  e.  Ordinarily,  the  cut  taken  is  a draw  cut, 
the  cutter  being  drawn  across  the  face  of  the  blank;  the 
machine  can  readily  be  used,  however,  for  pushing  the  cut- 
ter across  the  blank.  The  stroke  of  the  ram  is  adjustable 
for  length  and  position. 

49.  Internal  gears  can  be  cut  with  the  same  ease  as 
spur  gears  by  means  of  this  machine,  and  the  cutter  will 
automatically  produce  teeth  conjugate  to  itself  and  to  any 


GEAR-CUTTING. 


25 


§ 18 

spur  gear  cut  by  the  same  cutter.  Sprocket  wheels  can  also 
be  cut  by  using  a suitably  formed  cutter. 

50.  The  cutter  is  a spur  gear  having  excessive  adden- 
dum on  one  side  and  excessive  dedendum  on  the  other, 
causing  it  to  look  like  a bevel  gear.  As  is  well  known,  any 
planing  tool  must  have  clearance  in  order  to  cut;  this  cutter 
is  no  exception  to  the  general  rule,  and  is  given  clearance 


by  making  it  like  a bevel  gear.  It  is  sharpened  by  grinding 
its  top  face  in  a special  grinding  machine;  while  it  is  true 
that  this  grinding  will  change  the  pitch  of  the  cutter,  the 
fact  remains  that,  owing  to  the  small  inclination  of  the 
teeth,  the  reduction  in  pitch  will  be  so  extremely  small  as 
to  be  negligible  for  all  practical  purposes. 


26 


GEAR-CUTTING. 


§ 18 

SINGLE-TOOTH  MOLDING-PLANING  PROCESS. 

51.  Development  of  tlie  Process.  — As  previously 
explained,  in  the  molding  process  the  teeth  of  a gear  are 
formed  by  running  a rack  over  the  gear  blank,  as  is  shown 
in  Fig.  13  (a).  It  is  readily  seen  that  this  operation  may  be 


reversed;  that  is,  the  rack  may  remain  stationary  and  the 
gear  blank  may  be  rolled  along  it  in  order  that  teeth  conju- 
gate to  those  of  the  rack  may  be  generated.  This  is  shown 
in  Fig.  13  ( b ). 

52.  The  rack  may  be  replaced  by  a single  stationary 
tooth,  as  illustrated  in  Fig.  14;  then,  if  the  gear  blank  is 
rolled  past  this  tooth  with  a motion  equivalent  to  that  of  a 
pinion  rolling  in  a rack,  the  single  tooth  will  . mold  opposite 
sides  of  two  future  adjacent  teeth  to  a form  conjugate  to  its 
own.  Fig.  14  ( a ) shows  the  position  of  the  molding  tooth 
when  it  first  engages  the  gear  blank,  which  is  rolled  in  the 
direction  of  the  arrow  x and,  consequently,  advances  along 
the  straight  line  a b in  the  direction  of  the  arrow  y.  In 


18 


GEAR-CUTTING. 


27 


Fig.  14  ( b ),  the  blank  has  been  rolled  into  the  position 
shown,  its  original  position  being  given  by  the  dotted 
circle  c.  The  center  d of  the  gear  blank  is  here  perpendicu- 
larly below  the  molding  tooth,  and  the  face  of  one  tooth 
and  the  flank  of  another  have  been  fully  formed.  In 
Fig.  14  (c),  the  blank  has  been  rolled  forwards  until  the 


molding  tooth  is  about  to  leave  the  blank,  and  the  opposite 
faces  of  two  future  adjacent  teeth  have  been  fully  formed; 
that  is,  one  space  has  been  molded.  In  order  to  show  the 
rotation  and  advance  of  the  blank  more  clearly,  several  of 
its  different  positions  are  given;  the  dotted  circle  c repre- 
sents the  position  occupied  in  Fig.  14  ( a ),  and  the  dotted 
circle  c'  gives  the  position  shown  in  Fig.  14  ( b ). 

53.  Since  a single-tooth  molding  tool  can  finish  only 
one  space  at  a time,  it  follows  that  after  each  passage  of  the 
tool,  the  blank  must  be  rotated  by  a suitable  indexing 
mechanism  through  an  angle  corresponding  to  one  tooth. 

54.  The  single  molding  tooth  may  be  made  in  the  form 
of  a planer  tool  and  may  then  be  given  a reciprocating  mo- 
tion across  the  face  of  the  blank;  after  it  has  cleared  the 
blank  on  the  return  stroke,  the  blank  may  be  revolved  and 
advanced  forwards  a little  and  the  tool  be  reciprocated 
through  it  again.  This  cycle  of  operations  being  repeated 
until  the  tool  does  not  engage  the  blank  any  more,  the  op- 
posite sides  of  two  future  adjacent  teeth  are  thus  formed  by 
successive  cuts  to  be  conjugate  to  the  gear-tooth  repre- 
sented by  the  planing  tool. 


28 


GEAR-CUTTING. 


§ 18 

55.  The  single-tooth  molding-planing  process  just  ex- 
plained forms  the  basis  of  a mechanical  method  of  correctly 
generating  the  teeth  of  bevel  gears  that  are  conjugate  to 
those  of  a circular  rack,  which  is  often  called  a crown 
gear.  The  principle  underlying  this  method  may  be  ex- 
plained as  follows:  When  a spur  gear  rolls  in  a rack,  its 
action  is  equivalent  to  that  of  the  pitch  cylinder  rolling 
without  slipping  on  the  pitch  plane  of  a rack,  and  the  path 


(a)  (b) 


Fig.  15. 

of  the  pitch  cylinder  will  be  represented  by  a straight  line. 
In  a bevel  gear  we  have  a pitch  cone  instead  of  the  pitch 
cylinder  of  the  spur  gear;  such  a cone  in  rolling  without 
slipping  on  a plane  surface  will  follow  a circular  path,  and 
the  apex  of  the  cone  will  coincide  with  the  center  of  the  cir- 
cle representing  the  path,  as  is  shown  in  Fig.  15  ( a ).  From 
this  it  follows  that  the  rack  for  a bevel  gear  must  be  circu- 
lar, as  is  shown  in  Fig.  15  ( b ). 

56.  Obviously,  a circular  rack  may  be  used  for  molding 
the  teeth  of  a bevel  gear  in  the  same  manner  in  which  a 
straight  rack  may  be  employed  for  generating  the  teeth  of 
a spur  gear,  rolling  the  bevel-gear  blank  along  the  circular 
rack  just  as  the  pitch  cone  in  Fig.  15  (a)  would  roll  without 
slipping  on  the  plane  surface  representing  the  pitch  plane 
of  the  rack.  As  was  explained  in  connection  with  spur 
gears,  the  rack  may  be  replaced  by  a single  tooth;  when 
transforming  the  molding  tooth  into  a planing  tool,  how- 
ever, we  are  immediately  confronted  with  the  fact  that 
the  pitch  of  the  tooth,  and,  hence,  the  width  of  the  space 


§18 


GEAR-CUTTING. 


29 


between  two  teeth  of  a circular  rack,  changes  throughout 
the  length  of  the  tooth.  This  fact  precludes  the  possibility 
of  planing  opposite  sides  of  adjacent  teeth  in  one  cut. 

57.  In  a circular  rack,  neither  the  involute  nor  the  epi- 
cycloidal  form  of  tooth  can  be  planed  with  a formed  planing 
tool,  for  in  such  a rack  these  tooth  curves,  although  remain- 
ing symmetrical,  change  in  extent  throughout  the  length  of 
the  tooth.  This  method  was  employed  in  the  Bilgram  bevel- 
gear  cutting  machine  before  it  was  discovered  by  Mr.  Geo.  B. 
Grant  that  the  teeth  were  not  true  involute  teeth.  A cir- 
cular rack  having  its  teeth  planed  one  side  at  a time  with  a 
formed  tool  given  the  shape  of  an  involute  straight-rack  tooth, 
would  form  the  basis  of  a new  system  of  bevel-gear  teeth 
whose  sides  in  the  circular  rack  are  plane  surfaces,  and  to 
which  Mr.  Grant  has  given  the  name  of  octoidal  teeth. 


58.  The  octoidal  bevel-gear  tooth  (a  circular  rack  is 
here  considered  as  a special  form  of  a bevel  gear)  being 
formed  by  a tool  having  the  shape  of  an  involute  straight- 
rack  tooth,  it  naturally  has  the  same  general  form  as  the  true 
involute  bevel-gear  tooth,  and,  hence,  has  been,  and  is  yet, 
confounded  with  it  by  many  writers  on  the  subject  of  gear- 
cutting. 


D 


59.  Since  a circular  rack  may  generate  teeth  conjugate 
to  its  own  by  molding,  it  is  a logical  conclusion  that  the 
molding  process  may  be  replaced  by  the  molding-planing 
process,  as  is  done  in  the  case  of  spur  gears  generated  by 
a straight  rack.  Instead  of  planing  parallel  to  the  axis 
of  a pitch  cylinder,  however,  the  planing  of  a bevel  gear 
must  be  done  toward  the  apex  of  its  pitch  cone,  and  the 
planing  tool  must  move  parallel  to  the  bottom  of  the  teeth, 
as  is  done  in  planing  the  crown  gear. 


60.  The  planing  tool  is,  in  practice,  made  slightly  nar- 
rower than  the  width  of  the  space  between  teeth  at  their 
smaller  end;  it  is  then  reciprocated  through  the  gear  blank 
in  the  same  direction  that  the  sides  of  the  teeth  of  a circular 
rack  occupy;  that  is,  radially  toward  the  center  of  the  rack 


GEAR-CUTTING. 


§18 


30 

and,  hence,  toward  the  apex  of  the  pitch  cone.  After  each 
cut,  the  gear  blank  is  given  a motion  equivalent  to  that  of 
its  pitch  cone  rolling  on  the  pitch  plane  of  a circular  rack; 
by  successive  rollings  of  the  blank  and  passages  of  the  cut- 
ting tool  through  it,  one  side  of  one  tooth  is  made  conjugate 
to  the  side  of  the  tooth  of  a circular  octoidal  rack.  By  suit- 
able indexing  and  a repetition  of  the  forming  operation  for 
the  opposite  side  of  each  tooth,  a correct  octoidal  bevel  gear 
is  cut  that  has  teeth  conjugate  to  those  of  the  corresponding 
circular  rack;  consequently,  both  bevel  gears  of  a pair  thus 
cut  have  teeth  that  are  conjugate  to  one  another,  and,  hence, 
will  run  together  correctly. 


61.  Bilgram  Uevel-Gear  Cutter. — The  method  of 
generating  conjugate  bevel-gear  teeth  that  has  been  just 


18 


GEAR-CUTTING. 


31 


explained  is  employed  in  the  Bilgram  bevel-gear-cut- 

ting  machine  shown  in  perspective  in  Fig.  16.  In  this 
machine,  the  planing  tool  a , which  is  formed  to  conform  to 
the  sides  of  the  teeth  of  a circular  involute  rack,  is  held  in 
the  tool  post  of  a crank-driven  ram  £.that  reciprocates  in 
suitable  guides  formed  in  the  frame  of  the  machine.  The 
tool  post  is  set  into  a clapper  similar  to  that  of  a planer  head, 
in  order  to  allow  the  tool  to  swing  away  from  the  work  on 
the  return  stroke. 

62.  The  gear  blank  receives  a rolling  motion  from  a 
very  interesting  piece  of  mechanism.  The  gear  blank  c is 
mounted  upon  a spindle  e.  The  axis  f g of  the  spindle  e in- 
tersects an  axis  h i passing  through  the  bearings  j and  k. 
The  piece  n is  made  in  the  form  of  a portion  of  a conical 
surface,  the  apex  of  the  cone  being  at  the  intersection  of 
the  axes  f g and  Jii.  About  this  conical  surface  two  bands 
l and  m are  arranged  so  that  as  the  portion  of  the  machine 
carrying  the  axis  f g is  swung  backwards  and  forwards  the 
bands  / and  in  will  cause  the  spindle  e to  rotate  about  the 
point  where  the  axes  f g and  h i intersect.  By  properly 
adjusting  the  gear  c,  so  that  the  tool  a travels  in  the  direc- 
tion of  the  bottom  of  the  gear  teeth,  the  machine  will  be  so 
set  that  the  rotating  of  the  conical  surface  n will  cause  the 
gear  c to  rotate  as  though  it  were  in  contact  with  a gear 
tooth  represented  by  the  tool  a . 

63.  The  machine  is  provided  with  such  adjustments 
that  the  gear  blank  c can  always  be  brought  into  the  proper 
relation  to  the  cutting  tool  a , without  the  necessity  of 
having  the  piece  n constructed  as  a cone  having  the  same 
central  angle,  the  only  requirement  being  that  the  conical 
piece  n shall  give  the  axis  fg  the  proper  rotation  about  the 
intersection  of  the  two  axes  fg  and  hi.  The  effect  of  the 
motion  is  the  same  as  if  the  bevel  gear  c were  rolling  upon  a 
circular  rack,  one  tooth  of  which  is  represented  by  the  cut- 
ting tool  a.  A suitable  indexing  mechanism  spaces  the  teeth 
correctly  and  an  automatic  feed  mechanism  rolls  the  blank 
slightly  after  each  return  stroke  of  the  forming  tool  a. 


32 


GEAR-CUTTING. 


18 


MOLDING-MILLING  PROCESS. 

64.  Principle  of  Operation. — The  principle  of  opera- 
tion underlying  the 


molding-millingproc- 
ess  is  illustrated  by 
the  aid  of  Fig.  17. 
Equal  cutters  a , a , 
in  series,  the  profile 
of  each,  of  which  is 
the  same  as  that  of 
a rack  tooth,  are 
placed  alongside  one 
another  on  a man- 
drel and  at  a distance 
from  one  another 
equal  to  the  circular 
pitch,  so  that  a longi- 
tudinal section  taken 
through  all  the  cut- 
ters shall  have  the 
outline  of  the  teeth 
of  a rack.  The  num- 
ber of  cutters  is  made 
equal  to  the  number 
of  teeth  the  pro- 
posed gear  is  to  have. 
The  gear  blank  b is 
mounted  on  an  arbor 
at  right  angles  to 
the  axis  of  rotation 
of  the  cutters,  and 
the  gear  blank  and 
cutter  arbor  are  so 
connected  by  gearing 
that  when  the  blank 
rotates  in  the  direc- 
tion of  the  arrow  x , 
the  cutter  arbor  will 


GEAR-CUTTING. 


33 


§ 18 

advance  in  the  direction  of  the  arrow  y at  exactly  the  same 
velocity;  that  is,  the  cutter  arbor  and  gear  blank  will  move 
in  relation  to  each  other  exactly  as  if  they  were  a rack  and 
pinion  in  mesh. 

65.  Let  the  gear  blank  and  cutter  be  brought  together 
as  shown  in  the  end  view,  the  cutter  revolving  about  its 
axis  and  cutting  into  the  blank.  Then,  if  the  blank  is  ro- 
tated at  the  same  time  that  the  cutter  is  moved  in  the  direc- 
tion of  its  axis,  the  cutter  teeth  will  cut  out  grooves  in  such 
a manner  that  their  profile  in  the  plane  r s will  be  that  of 
teeth  conjugate  to  those  of  the  rack  represented  by  a longi- 
tudinal section  of  the  cutter.  When  the  blank  has  revolved 
one  turn,  let  the  cutter  and  the  blank  be  separated;  return 
the  cutter  to  its  original  position ; bring  the  blank  and  cut- 
ter together  again,  and  feed  the  cutter  over  the  blank  until 
the  cutting  is  done  in  a plane  t u slightly  in  advance  of  r s. 
After  this  cut  has  been  taken  all  around  the  blank,  let  the 
cycle  of  operations  be  repeated  again  and  again  until  the 
cutter  has  been  clear  across  the  face  of  the  gear  blank.  The 
teeth  thus  produced  will  be  conjugate  to  those  of  the  rack 
whose  profile  is  given  by  a longitudinal  section  of  the  cutter. 

66.  Swasey  Cutter. — The  practical  objections  to  the 
method  of  procedure  just  explained  are  the  great  number 
of  cutters  required  and  the  deflection  of  the  arbor  on  which 
they  are  carried.  These  objections  have  been  overcome 
in  an  ingenious  manner  by  Mr.  Ambrose  Swasey,  and  the 
process  has  thus  been  made  mechanically  practical. 

An  end  view  and  partial  sectional  elevation  of  the  Swasey 
cutter  is  shown  in  Fig.  18.  Each  cutter  is  seen  to  be 
divided  into  two  parts,  and  the  cutters  are  all  connected 
together  into  two  independent  sections,  each  of  which  is 
mounted  on  two  cylindrical  rods  passing  through  the  holes 
shown.  The  four  rods  pass  through  cylindrical  sleeves  at 
each  side  of  the  cutters;  the  holes  in  the  sleeves  through 
which  the  rods  pass  are  placed  in  such  a relation  to  the  axis 
of  the  sleeves  that  upon  revolving  them  the  cutters  will  run 
true.  Each  section  of  cutters  is  moved  in  the  direction  of 


34 


GEAR-CUTTING. 


§ 18 

the  axis  by  a cam  at  the  same  time  that  they  revolve;  as 
soon  as  one  section  during  its  revolution  has  cleared  the 
gear  blank,  the  cam  throws  it  back  to  its  original  position, 
and  just  before  commencing  to  cut  it  begins  to  slide  forwards 


Fig.  18. 

again  at  a velocity  equal  to  that  of  a point  on  the  pitch  circle 
of  the  gear  blank.  It  will  be  understood  that  while  one 
section  of  the  cutters  is  engaged  with  the  blank,  the  section 
clear  of  the  blank  is  being  returned  to  its  original  position^ 

67.  The  motion  of  each  section  of  the  cutter  during  one 
of  its  revolutions  can  be  easier  understood  by  simply  con- 
sidering the  motion  of  a point  on  the  periphery  of  one  cutter 


in  one  section.  For  instance,  consider  the  point  a in  Fig.  19, 
where  the  circle  b represents  the  periphery  of  the  cutter. 
Then,  as  this  point  remains  at  a constant  distance  from  the 


GEAR-CUTTING. 


35 


§18 

axis  of  rotation  represented  by  the  point  c,  it  follows  that 
during  any  axial  movement  the  point  a will  follow  a path 
lying  on  the  surface  of  a cylinder,  as  degf.  Let  the  point 
whose  motion  we  are  considering  be  at  a'  on  the  surface  of 
the  cylinder.  Then,  as  soon  as  the  gear  blank  and  cutter 
begin  to  move  in  respect  to  each  other,  the  point  a'  during 
the  rotation  and  axial  advance  of  the  cutter  follows  the 
right-handed  helical  path  a'  h i in  the  direction  given  by  the 
arrows.  When  the  point  a'  reaches  the  position  i,  the  cam 
constraining  the  axial  motion  of  the  cutter  commences  to 
return  it  to  its  original  position,  and  the  point  whose  motion 
we  are  considering  returns  along  the  left-handed  helical 
path  ika!  to  its  starting  point  a’. 

68.  By  timing  the  action  of  the  two  sections  in  such  a 
manner  that  when  one  is  at  the  limit  of  its  forward  travel 
and  about  to  return,  the  other  section  is  just  beginning  to 
travel  forwards,  the  cutting  action  of  the  two  sections  is 
made  equivalent  to  that  of  an  infinite  number  of  equal  cut- 
ters, similar  to  those  shown  in  Fig.  17,  placed  alongside  each 
other.  After  the  Swasey  cutters  have  passed  once  clear 
around  the  wheel  that  is  being  cut,  the  cutters  are  advanced 
a little  in  front  of  the  plane  in  which  the  cut  just  finished 
was  taken  and  the  new  cut  is  taken  all  around  the  gear  blank 
again.  This  cycle  of  operations  is  repeated  automatically 
until  the  cutters  have  been  across  the  whole  face  of  the 
wheel. 


69.  The  Swasey  process  of  generating  gear-teeth  in- 
volves the  use  of  a special  machine.  In  this  machine  the 
cutter  and  the  gear  blank  are  connected  together  in  such  a 
manner  that  the  cutter  makes,  during  each  revolution  of  the 
gear,  a number  of  revolutions  exactly  equal  to  the  number 
of  teeth  which  the  gear  to  be  cut  is  intended  to  have.  While 
this  is  unnecessary  in  the  process  described  in  Art.  64,  it  is 
absolutely  essential  with  the  modified  cutters  used,  in  order 
that  the  cams  giving  the  axial  motion  to  the  cutter  sections 
shall  time  the  motions  correctly. 


36 


GEAR-CUTTING. 


§ 18 

70.  Molding-Milling  Bevel  Gears.  — A molding- 
milling process  for  generating  octoidal  bevel-gear  teeth  has 
recently  been  brought  out  by  Mr.  Warren,  and  a number  of 
special  machines  for  it  have  been  built  by  The  Pratt  & 
Whitney  Company,  of  Hartford,  Connecticut.  This  proc- 
ess is  based  on  the  Bilgram  bevel-gear  planing  process;  a 
milling  cutter  having  a section  equal  to  that  of  an  involute 
straight-rack  tooth  is  substituted  for  the  planing  tool,  how- 
ever. The  gear  blank  is  given  the  same  rolling  motion  as  is 
done  in  the  Bilgram  machine,  and  octoidal  teeth  conjugate 
to  those  of  a" circular  rack  are  formed.  In  this  process,  two 
milling  cutters  are  employed,  in  order  to  finish  both  sides  of 
a tooth  at  once;  their  lines  of  motion  converge  toward  the 
apex  of  the  pitch  cone. 


MAKING  WORM-WHEELS. 

71.  I n practice  worm-wheels  are  cut  either  approxi- 
mately or  exactly  correct.  In  the  former  case,  a formed 
involute  spur-gear  cutter  having  a designating  mark  cor- 
responding to  the  number  of  teeth  equal  to  the  number 
of  turns  of  the  worm  for  one  revolution  of  the  worm-wheel, 
is  used;  in  the  latter  case,  a special  rotary  cutter,  called  a 
hob,  is  employed,  and  generates  teeth  conjugate  to  its  own. 

72.  Cutting  With  a Formed  Cutter. — When  a 
formed  cutter  is  used,  the  teeth  are  generally  cut  in  a 
straight  path  diagonally  across  the  face  at  an  angle  corre- 
sponding to  that  of  the  worm,  but  otherwise  cutting  the 
worm-wheel  as  if  it  were  a spur  gear.  In  practice,  the 
angle  that  the  teeth  make  with  the  axis  of  the  worm-wheel 
is  found  by  trial;  the  index  head  of  the  universal  milling 
machine  is  swiveled  on  its  table  for  this  purpose  and  a few 
teeth  are  cut.  The  worm  is  then  tried  in  these  teeth  to  see 
whether  its  axis  is  at  right  angles  to  that  of  the  worm- 
wheel;  the  setting  is  changed  if  this  is  not  the  case.  Owing 
to  the  liability  of  spoiling  the  gear  blank  by  these  trial  cuts, 
it  is  recommended  to  use  a hardwood  blank  of  the  same  size 
to  experiment  on. 


GEAR-CUTTING. 


37 


18 


73.  Hobbing. — Hobbing  will  produce  the  best  worm- 
wheel,  and  is  the  process  that  should  al- 
ways be  employed  for  a wheel  subjected 
to  much  use.  The  hob  is  shown  in 
Fig.  20.  It  will  be  noticed  that  it  is 
nothing  but  a worm  that  has  been  ser- 
rated in  order  to  form  cutting  edges.  In 
order  that  the  thread  of  the  worm  may 
clear  the  bottom  of  the  corresponding 
spaces  in  the  worm-wheel,  the  thread  of  the  hob  is  made 
slightly  higher  than  that  of  the  worm. 


74.  In  hobbing  a worm-wheel,  the  wheel  is  placed  on  an 
arbor  between  the  centers,  but  is  not  confined  by  a dog,  so 
that  it  is  free  to  rotate  about  its  axis.  The  hob  is  placed 
at  right  angles  to  the  axis  of  rotation  of  the  worm-wheel  and 


while  revolving  is  sunk  into 

A 


B 

Fig.  21. 

index  for  the  number  of  teeth 
The  milling-machine  table,  aft< 


the  face  of  the  worm-wheel 
to  the  desired  depth.  The 
hob,  in  continuing  to  re- 
volve, rotates  the  worm- 
wheel  and  cuts  its  teeth  to 
a shape  conjugate  to  that 
of  its  own. 

75.  A worm-wheel  that 
is  to  be  hobbed  should  al- 
ways be  prepared  for  hob- 
bing by  notching  it  with  an 
involute  cutter  slightly  nar- 
rower than  the  face  of  the 
hob  teeth.  This  process  is 
called  gashing,  and  is 
done  in  a horizontal  ma- 
chine as  follows : The  blank 
is  mounted  on  an  arbor  and 
placed  between  index  cen- 
ters, which  are  arranged  to 
the  worm-wheel  is  to  have, 
r being  set  to  zero,  is  moved 


38 


GEAR-CUTTING. 


§ 18 

horizontally  until  the  axis  A B oi  the  cutter  is  in  the  central 
plane  of  the  worm-wheel,  as  shown  in  Fig.  21.  The  table 
is  then  swung  on  the  saddle  until  the  angle  B O E corre- 
sponds approximately  to  the  angle  of  the  helix  of  the  worm, 
and  the  notches  are  cut,  raising  the  knee  by  means  of  the 
vertical  feed.  The  table  is  then  swung  back  to  zero  and 
the  hob  is  used  for  finishing  the  teeth.  Since  the  worm- 
wheel  is  driven  by  the  hob,  the  notches  must  be  deep 
enough  and  wide  enough  to  insure  good  driving  when  the 
hob  is  first  applied.  If  hobbing  is  attempted  without  pre- 
vious gashing,  it  will  often  happen  that  a greater  number 
of  teeth  than  is  desired  will  be  obtained. 

76.  In  machines  designed  especially  for  cutting  worm- 
gears,  the  hob  and  wheel  blank  are  connected  together  by 
gearing  that  drives  the  wheel  blank  at  the  proper  speed. 
Gashing  may  be  omitted  in  such  machines,  since  the  change 
gears  insure  a correct  spacing  of  the  worm-wheel  teeth. 


EXAMPLES  OF  SPECIAL  CASES  OF  CONJUGATE  GEARS. 

77.  Spiral  Bevel  Gears.  — Fig.  22  shows  a pair  of 
miter  gears  with  the  teeth  planed  in  a spiral,  so  that  one 

tooth  shall  always  be  in  deepest 
contact  when  the  gears  work  to- 
gether. These  gears  work  together 
almost  perfectly;  in  fact,  uneven- 
ness cannot  be  detected  by  obser- 
vation. The  term  herring-bone 
gears  has  been  applied  to  them. 
Their  surfaces  are  not  warped  but 
are  truly  conical,  so  that  the 
shafts  are  in  the  same  plane  and 
at  right  angles  to  each  other. 

78.  Special  Bevel  Gears. — The  four  beveL  gears 
working  together,  shown  in  Fig.  23,  are  somewhat  remark- 
able, as  it  was  for  a long  time  thought  impossible  to  make 
such  gears  so  that  they  would  work  together  properly.  The 


GEAR-CUTTING. 


39 


§ 18 

gear- model  here  shown  was  made  by  Mr.  Hugo  Bilgram  on 
the  machine  shown 
in  Fig.  16.  The  large 
gear  has  36  teeth, 
the  others  12,  18, 

and  24  teeth.  The 
36-tooth  and  18-tooth 
gears  mesh  together 
correctly,  according 
to  the  ordinary 
method  of  design.  In 
order  that  the  two 
pitch  cones  of  bevel  gears  shall  roll  together  without  slip- 
ping, their  vertices  must  meet  in  a point. 

The  diagram  of  four  pitch  cones  in  Fig.  24  ( a ) shows  how 
the  pitch  cones  of  the  gears  shown  in  Fig.  23  would  lie  with 

respect  to  one  another  in 
ordinary  practice.  The 
two  cones  a and  b would 
roll  together  without  slip- 
ping, but  c and  d would 
not  roll  on  a without  slip- 
ping. In  order  to  make 
the  gears  so  that  they 
would  have  a constant 
velocity  ratio,  some  part 
of  the  teeth  must  have 
moved  as  if  the  pitch 
cones  slipped  on  each 
other,  but  in  correctly 
formed  gears  the  pitch 
circles  must  roll  together 
without  slipping.  The 
manner  in  which  this  is 
accomplished  is  illustrated  in  Fig.  24  ( b ).  The  gears  a and  b 
will  roll  together  properly  as  their  pitch  cones  meet  at  the 
point  of  intersection  of  their  axes,  but  the  vertex  of  the 
cone  c , Fig.  24  (a),  does  not  come  to  the  same  point.  New 


40 


GEAR-CUTTING. 


§ IB 

pitch  cones  must  therefore  be  assumed,  which  changes  the 
relation  of  the  addendum  and  dedendum  of  the  teeth  at 
different  points  of  their  length.  There  will  be  the  least 
variation  when  the  middle  of  the  tooth  has  correct  adden- 
dum. The  large  end  of  the  teeth  of  the  gear  c will  have 
excessive  addendum,  as  shown  in  Fig.  24  ( b ),  and  the  small 
encJ  will  have  excessive  dedendum,  but  diminished  adden- 
dum. If  the  gear  c had  been  larger  than  the  gear  a , the 
conditions  would  have  been  reversed.  It  would  seem  diffi- 
cult to  produce  such  teeth  so  that  the  gears  would  run 
together  smoothly,  but  it  has  been  done.  The  machine 
shown  in  Fig.  16  was  used  with  slight  variations,  most  of 
which  were  merely  adjustments.  The  gears  run  very 
smoothly,  indeed.  These  gears  have  proved  very  useful  in 
certain  special  machines.  The  limit  of  variation  from  the 
standard  bevel  gears  is  reached  when  the  flanks  of  the  teeth 
become  too  much  undercut. 


GRINDING. 

(PART  1.) 


INTRODUCTION. 

1.  Definition  of  Grinding. — Generally,  the  term 
“ grinding  ” is  used  to  designate  the  operation  of  reducing  a 
substance  to  a powder  by  friction  or  trituration.  It  is  also 
used  to  designate  the  act  of  sharpening  tools.  In  the 
present  section,  it  will  be  understood  to  mean  the  polishing, 
finishing,  or  sharpening  of  tools  or  metal  parts  (mostly  hard- 
ened steel)  by  means  of  revolving  wheels  composed  of  or 
covered  with  angular  grains  of  some  abrading  material  that 
is  harder  than  the  substance  to  be  cut. 

The  grinding  process  is  characterized  by  the  fact  that  the 
material  removed  is  all  reduced  to  a fine  powder,  and  on  this 
account  the  amount  of  power  necessary  to  remove  a given 
weight  of  material  by  grinding  is  greater  than  would  be  the 
case  with  a machine  tool  that  produced  larger  chips. 

2.  Grinding  Materials. — All  grinding  is  done  by  the 
angular  grains  of  some  hard  substance  that  are  held  in  place 
while  doing  the  grinding  by  being  bedded  in  a softer  sub- 
stance, or  that  are  so  cemented  or  united  together  as  to 
form  a wheel  or  a rectangular  mass. 

Most  grinding  materials  are  used  in  the  form  of  wheels, 
and  may  be  divided  into  the  two  classes,  grindstones  and 
grinding  wheels,  the  latter  including  all  emery,  corundum, 
and  carborundum  wheels.  There  is  another  small  class  that 
would  then  come  under  the  heading  of  oilstones. 

§ 18 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 

C.  5*.  III. — 2 


2 


GRINDING. 


§18 


GRINDSTONES  AND  OILSTONES. 


GRINDSTONES. 

3.  Composition. — In  the  case  of  grindstones,  the  cut- 
ting material  is  oxide  of  silica  SiO„  or  quartz  sand , as  it  is 
commonly  called.  The  individual  grains,  in  order  that  they" 
may  be  in  proper  condition  for  cutting,  must  be  sharp  and 
angular.  As  found  in  nature,  the  grains  are  bound  together 
either  by  a calcareous  or  lime  cement,  or  by  a silicate  bond. 
This  bond  must  be  of  such  nature  and  strength  that  when 
the  grains  of  sand  become  dull,  the  friction  will  tear  them 
from  the  stone  and  thus  uncover  fresh,  sharp  grains  for  the 
work  of  grinding.  Grindstones  are  simply  natural  sand- 
stones of  such  texture  that  they  are  suitable  for  grinding 
operations. 

4.  Localities  Where  Grindstones  Are  Obtained. 

Many  of  the  best  grindstones  used  in  the  United  States 
come  from  Berea,  Ohio;  Huron,  Michigan;  or  from  Grind- 
stone Island,  Nova  Scotia.  All  these  localities  produce 
several  grades  of  stones;  the  Nova  Scotia  stones  are  of  all 
grades,  but  most  of  the  Berea  stones  are  rather  coarse. 
There  are  also  a few  foreign  stones  used  in  the  United 
States,  most  of  which  are  known  as  Liverpool  stones.  The 
Liverpool  stones  vary  in  quality  from  medium  to  fine. 

5.  Action  of  Water  On  a Grindstone. — As  grind- 
stones cut  more  freely  when  wet,  they  are  generally  used 
with  water.  The  function  of  the  water  is,  further,  to  carry 
off  the  heat  resulting  from  the  friction  between  the  stone 
and  the  tool,  and  also  to  wash  away  any  particles  of  the 
stone  and  the  steel  that  are  dislodged  by  the  grinding,  and 
that,  if  not  carried  away,  would  tend  to  fill  up  the  small 
spaces  between  the  grains  of  the  grindstone,  and  thus  glaze 
its  surface. 

Grindstones  are  softer  when  wet  than  when  dry,  and, 
hence,  a grindstone  should  not  be  left  standing  with  only 
one  side  in  water,  as  this  will  cause  the  wet  side  to  be  worn 


18 


GRINDING. 


3 


away  faster  than  the  other  when  the  stone  is  again  used. 
This  is  a point  that  should  be  carefully  noted. 

6.  Grade  of  Stone  Required  for  Thin  Work. — For 

grinding  such  pieces  as  mowing-machine  knives,  or  any  other 
piece  having  sharp  thin  edges  that  the  stone  must  cut  freely 
in  order  not  to  heat  the  work  and  draw  the  temper,  it  is  nec- 
essary that  the  stone  be  soft  enough  to  wear  away  with  such 
rapidity  as  to  keep  the  cutting  particles  at  the  grindstone 
surface  always  sharp. 

7.  Tool  Rests  for  Grindstones.  — For  general  tool 
grinding,  a rest  is  commonly  used.  A temporary  or  movable 
rest,  such  as  a block  of  wood,  is  regarded  by  some  mechan- 
ics as  being  the  most  desirable,  because  in  case  the  tool  should 
catch,  the  rest  would  be  thrown  out,  and  the  damage  to  the 
stone  or  to  the  operator  would  be  less  than  if  a solid,  per- 
manent rest  were  used. 

8.  Grindstone  Mountings. — In  mounting  the  stone, 
it  is  desirable  to  use  iron  flanges,  about  one-third  the  diam- 
eter of  the  stone,  that  are  so  hollowed  on  the  inside  as 
to  bear  upon  the  stone  for  an  inch  or  more  near  their  per- 
ipheries. It  is,  however,  quite  common  to  mount  the  stone 
without  flanges,  in  which  case  the  stone  has  a square  hole 
in  its  center,  and  the  shaft,  which  is  also  square  where  it 
passes  through  this  hole,  is  surrounded  by  a bushing  of  wood 
or  babbitt.  The  accompany- 
ing illustration,  Fig.  1,  shows 
a grindstone  mounted  upon 
a frame  that  has  a trough 
for  water,  and,  also,  a truing 
device  attached  to  it. 

9.  Automatic  Tru- 
ing Device. — The  truing 
device  shown  on  the  frame 
in  Fig.  1 works  automatic- 
ally, and  can  be  applied 
while  the  grindstone  is  in 


4 


GRINDING. 


§ 18 

use,  and  removed  when  the  stone  has  been  trued.  It  is 
applied  to  the  face  of  the  stone  that  moves  upwards.  By 

turning  the  hand  wheel  a, 
the  threaded  roll  is  brought 
into  contact  with  the  stone 
and  kept  there  until  the  stone 
is  trued,  the  water,  mean- 
while, being  left  in  the 
trough.  When  the  screw 
threads  become  dull,  they 
can  be  recut.  Fig.  2 shows 
the  truing  device  apart  from 
the  frame,  b being  the  threaded  roll. 

1().  Truing  by  Hand. — All  grindstones  work  out  cf 
true,  and  in  the  absence  of  an  automatic  truing  device,  the 
stone  is  sometimes  trued  by  the  use  of  an  old  file  and  a 
piece  of  gas  pipe,  or  by  using  a piece  of  gas  pipe  alone.  If 
the  stone  is  badly  out  of  true,  it  will  be  well  to  turn  off  the 
surface  with  the  tang  of  an  old  file  held  firmly  on  a rest 
against  the  face  of  the  stone,  as  shown  in  Fig.  3 ( a ).  This 
will  remove  the  high  parts  of  the  stone  quickly,  but  will 
leave  the  surface  quite  rough.  A smooth  surface  may  then 
be  produced  by  turning  the  face  with  a piece  of  gas  pipe, 
the  size  that  is  commonly  used  being  f-inch  to  f-inch  pipe. 
The  pipe  is  held  on  the  rest  but  rolled  across  the  face  of 


the  stone,  as  shown  at  Fig.  3 ( b ).  The  finishing  and  turn- 
ing on  the  stone  is  really  done  by  the  sand  that  is  cut  from 
the  face  of  the  stone  and  that  lodges  in  the  soft  iron  of  the 
pipe,  so  that  the  process  is  actually  that  of  stone  cutting 


§18 


GRINDING. 


5 


stone.  In  both  cases,  the  stone  should  revolve  in  the  direc- 
tion indicated  by  the  arrow. 

11.  Speed  Used  in  Grinding  Tools.  — For  tool 
grinding,  the  grindstones  are  run  at  much  less  than  their 
maximum  speed.  For  machinists’  tools,  the  peripheral  speed 
should  be  800  to  1,000  feet  per  minute;  for  carpenters’ 
tools,  550  to  600  feet  per  minute.  Another  rule  frequently 
given  is  to  run  the  stone  at  the  highest  speed  at  which  the 
water  will  not  be  thrown  from  its  face  by  the  centrifugal 
force.  The  maximum  speed  is  limited  by  the  safe  working 
strength  of  the  stone. 

The  following  table  of  maximum  speeds  is  given  by  some 
authorities,  and  should  not  be  exceeded  except  when  a very 
hard,  strong  stone  is  used,  and  then  only  when  the  stone  is 
well  mounted  with  strong  flanges,  and  is  so  located  that 
damage  from  bursting  would  not  be  likely  to  be  very  great. 
The  number  of  revolutions  given  correspond  to  a periphery 
speed  of  nearly  3,400  feet  per  minute. 

TABLE  I. 


TABLE  OF  MAXIMUM  SPEEDS. 


Diameter  of  Stone. 

Revolutions  per 
Minute. 

8 feet 

135 

7 feet  6 inches 

144 

7 feet 

154 

6 feet  6 inches 

166 

6 feet 

180 

5 feet  6 inches 

196 

5 feet 

216 

4 feet  6 inches 

240 

4 feet 

270 

3 feet  6 inches 

308 

3 feet 

396 

6 


GRINDING. 


18 


12.  Artificial  Grindstones. — A few  artificial  grind- 
stones have  been  made  that  have  the  advantage  of  being 
more  uniform  in  texture  than  natural  stones.  At  the  pres- 
ent time,  most  of  the  artificial  grinding  disks  are  made  of 
emery  or  corundum,  and  are  generally  known  as  emery 
wheels.  They  have  largely  taken  the  place  of  sandstones 
for  grinding,  except  in  some  special  lines  of  grinding,  par- 
ticularly where  even  a little  heat  injures  the  work,  as  in 
the  grinding  of  glass  lenses. 


OILSTONES. 

1 3.  Composition. — Natural  oilstones,  like  grindstones, 
are  composed  of  quartz  sand  SiO 2,  but  the  grains  are  finer  and 
are  bound  together  in  a different  manner.  The  cementing 
material  or  bond  in  oilstones  is  generally  silica,  and  is  more 
in  the  nature  of  a glass  or  vitreous  bond  than  is  the  case 
with  grindstones.  In  fact,  most  oilstone  deposits  are  so 
seamed  with  thin  veins  of  quartz  that  it  is  impossible  to  get 
any  large  stones  or  slabs,  which  is  the  principal  reason  why 
grinding  wheels  are  not  made  of  this  material. 

The  oilstone  is  of  such  a nature  that  the  particles  worn 
from  the  stone  are  best  removed  by  oil  and  the  stone  cuts 
best  when  supplied  with  oil.  Generally  speaking,  sperm  oil 
is  the  best  grade  to  be  used  on  oilstones,  though  a good 
grade  of  machine  oil  can  also  be  used. 

14.  Kinds  and  Qualities. — The  classes  of  oilstones 
on  the  markets  in  the  United  States  may  be  generally 
divided  into  Arkansas  stones  and  Washita  stones.  The 
Arkansas  stones  are  very  fine-grained  and  appear  like  white 
marble.  They  are  used  for  sharpening  the  finer  grade  of 
instruments  and  produce  remarkably  keen,  fine  edges.  The 
Washita  stones  are  much  coarser  in  grain,  with  the  color 
sometimes  white,  but  frequently  having  a yellow  or  red 
tinge.  The  Washita  stone  is  coarser  than  the  Arkansas  and 
cuts  more  rapidly,  but  with  greater  delicacy  than  would 
ordinarily  be  expected  from  one  having  so  coarse  a grain. 


§18 


GRINDING. 


7 


The  Washita  stones  are,  as  a rule,  better  for  sharpening 
wood-working  tools  than  the  Arkansas  stones,  while  the 
Arkansas  stones  are  used  more  frequently  in  the  machine 
shop.  The  Washita  stones  can  be  obtained  in  larger  pieces 
than  the  Arkansas  stones  and  are  less  expensive. 

15.  Artificial  Oilstones. — Artificial  oilstones  are 
now  on  the  market.  They  possess  several  advantages  over 
the  natural  stones.  Those  sold  under  the  name  of  Indian 
oilstone  are  composed  of  a peculiar  grade  of  Indian  corun- 
dum, and,  hence,  have  very  good  cutting  qualities.  One. 
special  advantage  is  that  some  stones  are  manufactured 
having  one  coarse  face  and  one  medium  face,  i.  e.,  one  half 
of  the  stone  is  of  one  grade  and  the  other  half  of  another 
grade,  thus  giving  the  advantage  of  two  stones  with  only 
one  piece  to  look  after.  Then,  too,  the  artificial  stones  can 
be  made  in  special  forms,  such  as  slips,  cones,  etc.,  easier 
than  natural  stones.  The  artificial  oilstones  are  also  made 
in  any  size,  and,  as  a consequence,  the  larger  sizes  are  not 
extremely  expensive,  as  is  the  case  with  the  natural  stones. 
The  artificial  oilstones  are  also  made  in  the  form  of  wheels 
similar  to  emery  wheels,  and  either  in  the  form  of  wheels  or 
flat  slips,  they  can  be  used  with  oil  or  water  as  a lubricant. 
At  present  they  are  manufactured  in  three  grades:  fine, 
medium,  and  coarse.  The  fine  grade  is  approximately 
equivalent  to  the  Arkansas  stones,  the  medium  grade  to  the 
Washita  stones,  and  the  coarse  grade  cuts  freer  and  faster 
than  either  of  the  above. 


GRINDING  WHEELS. 


ABRASIVE  MATERIALS. 


CORUNDUM. 

16.  Composition  and  Where  Found. — Corundum 

is  pure  alumina,  or- oxide  of  aluminum.  It  is  crystalline  in 
structure,  and  has  a hardness  of  9,  in  this  respect  ranking, 
among  natural  minerals,  next  to  the  diamond. 


8 


GRINDING. 


§18 


Note. — In  order  to  provide  a convenient  means  of  comparing  the 
hardness  of  minerals,  a comparative  scale  has  been  adopted  in  which 
10  minerals  are  taken  to  represent  10  degrees  of  hardness,  and  all  other 
minerals  are  compared  with  the  members  of  this  scale.  The  scale  is 
as  follows: 


The  gem  sapphire  is  sometimes  used  in  the  scale  in  place  of  corun- 
dum, but  sapphire  is  only  the  gem  form  of  crystallized  corundum. 
Talc  is  the  softest  of  the  minerals  of  the  scale  and  can  easily  be 
scratched  with  the  finger  nail,  while  diamond  is  the  hardest  substance 
known. 

It  is  found  in  considerable  quantities  in  Georgia  and 
North  Carolina,  also  in  Canada;  while  small  quantities  have 
been  exported  from  India.  In  Georgia  and  North  Carolina, 
it  occurs  in  masses  in  veins  of  rock,  and  also  in  beds  in  the 
granular  form  known  as  sand  corundum.  In. the  latter  case 
it  is  mixed  with  clay  and  other  impurities.  In  Canada,  it  is 
found  quite  uniformly  distributed  through  large  masses  of 
rock  that,  when  crushed,  yields  10  percent,  to  20  percent,  of 
corundum  crystals. 

Good  commercial  corundum  shows  by  analysis  from 
40  per  cent,  to  80  per  cent,  or  even  90  per  cent,  of  the  thor- 
oughly crystallized  aluminum  oxide  A /2 09 ; from  5 per  cent,  to 
25  per  cent,  of  aluminum  silicate  and  imperfectly  crystallized 
aluminum  oxide;  from  2 per  cent,  to  6 per  cent,  of  iron 
oxide;  about  the  same  amount  of  free  silica;  and  from 
1 ^ per  cent,  to  3 per  cent,  of  water  or  other  substances  that 
are  driven  off  at  red  heat. 

1 7.  Properties. — When  corundum  occurs  in  masses,  it 
is  either  picked  up  on  the  surface  of  the  mountain  in 
boulders  of  various  sizes,  or  it  is  uncovered  by  blasting 
away  the  rock.  The  mineral  thus  obtained  is  passed 
through  crushers  and  then  through  rolls  until  it  is  reduced 
to  grains  of  suitable  size  for  making  wheels,  or  for  other 
abrasive  purposes.  Afterwards  it  is  frequently  treated  by 
an  abrading  and  washing  process  that  removes  the  impuri- 
ties from  the  grains  or  kernels  of  corundum.  It  is  then 


1.  Talc. 


6.  Feldspar. 

7.  Quartz. 

8.  Topaz. 

9.  Corundum  or  Sapphire. 

10.  Diamond. 


2.  Gypsum. 

3.  Calcite. 

4.  Fluorite. 

5.  Barite. 


GRINDING. 


9 


§ 18 

dried  and  graded  by  being  passed  over  sieves  of  suitable 
mesh  to  give  the  sizes  desired.  These  sizes  range  from 
Nos.  12  or  20  to  200. 

» 

18.  Grading,  and  Meaning  of  Numbers  Used. — 

The  numbers  by  which  the  grain  of  corundum  is  designated 
are  determined  as  follows:  A No.  20  sieve,  for  example,  is 
one  that  has  20  meshes  to  a lineal  inch,  and  No.  20  emery 
is,  theoretically,  composed  of  kernels  that  will  just  pass 
through  the  meshes  of  a No.  20  sieve.  Practically,  the  ker- 
nels of  No.  20  are  not  all  of  a size,  but  are  such  sizes  that 
the  largest  will  just  pass  through  a No.  20  mesh,  and  the 
smallest  will  not  pass  through  the  next  smaller-sized  mesh, 
which  may  be  that  of  a No.  22  or  24  sieve,  according  as  the 
grading  is  more  or  less  close  as  to  size.  The  numbers  prin- 
cipally used  for  making  abrasive  wheels  are  from  20  to  80 
or  100.  The  finer  numbers  are  used  for  polishing. 


EMERY. 

19.  Composition  and  Where  Found. — Emery  con- 
sists of  corundum  in  combination  with  the  protoxide  of 
iron.  The  presence  of  the  iron  gives  the  mineral  a dark 
color,  and  also  makes  the  grains  a little  tougher  and  less 
brittle  than  the  grains  of  pure  corundum.  In  hardness, 
emery  is  generally  rated  about  1 degree  lower  than 
corundum. 

The  principal  sources  of  commercial  emery  in  the  United 
States  are  the  extensive  emery  mines  at  Chester,  Massachu- 
setts, and  at  Peekskill,  New  York;  and  in  foreign  countries, 
the  island  of  Naxos,  belonging  to  Greece,  and  the  emery 
mines  of  Turkey,  located  near  Smyrna.  Good  commercial 
emery  has  from  40  per  cent,  to  60  per  cent,  of  solid  grains, 
the  remaining  60  per  cent,  to  40  per  cent,  being  aluminum 
silicate,  iron  oxide,  silica,  water,  etc.  in  proportions  that 
vary  with  the  kind  of  emery. 


10 


GRINDING. 


18 


20.  Preparation. — Emery  is  mined,  crushed,  cleaned, 
and  graded  in  about  the  same  manner  as  corundum,  and  is 
sold  in  the  market  as  Chester  emery,  Naxos  emery,  and 
Turkish  emery.  It  varies  considerably  in  its  degree  of 
purity,  there  being  a difference  in  the  quality  of  the  ore 
from  different  mines,  and  even  from  different  parts  of  the 
same  mine.  The  process  of  manufacture,  and  the  skill  and 
thoroughness  with  which  the  ore  is  treated  for  the  removal 
of  impurities,  also  have  much  to  do  with  its  degree  of 
purity. 


ARTIFICIAL  ABRASIVES. 

21.  Carborundum.  — The  electric  furnace  develops 
such  a high  temperature  that  it  offers  opportunity  for  ex- 
periments to  determine  whether  some  artificial  product  may 
be  produced  that  will  take  the  place  of  emery  and  corundum 
for  purposes  of  grinding.  In  1893,  Mr.  E.  G.  Acheson  pro- 
duced in  an  electric  furnace  a substance  that  he  named 
carborundum,  which  is  the  only  artificial  abrasive  that 
has  thus  far  been  extensively  used.  It  is  manufactured  in 
quite  large  quantities  by  The  Carborundum  Company  at 
Niagara  Falls.  Abrasive  wheels  are  made  of  this  material 
by  The  Carborundum  Company,  but  it  is  sold  in  the  market 
for  various  purposes,  though  not  for  the  manufacture  of 
wheels. 

Carborundum  is  carbide  of  silicon  SiC,  and  is  made  by 
surrounding  a small  core  or  cylinder  of  pure  carbon  with  a 
mass  of  coke  and  sand  to  which  a little  salt  and  sawdust  is 
added.  A powerful  electric  current  is  then  passed  through 
the  carbon  core,  which,  by  its  resistance  to  the  current,  be- 
comes heated  to  a high  temperature,  and  this  temperature 
is  communicated  to  the  coke  and  sand  surrounding  it.  At 
the  high  temperature  thus  obtained,  the  carbon  and  silicon 
unite  and  crystallize,  and  when  the  furnace  is  cooled  and 
the  core  uncovered,  it  is  found  to  be  surrounded  by  a ring 
of  brilliantly  colored  crystals  of  carborundum. 


GRINDING. 


11 


§18 


MANUFACTURE  ANI)  USE  OF  EMERY 
WHEELS. 

22.  Use  of  Term  Emery  Wheel. — In  speaking  of 
abrasive  wheels,  the  common  term  “emery  wheel”  will  in- 
clude also  corundum  and  carborundum  wheels,  except  where 
some  special  quality  requires  particular  mention  of  the 
cutting  material  of  the  wheel. 

23.  Parts  of  Emery  Wheel. — An  emery  wheel  con- 
sists of  two  essential  parts;  viz.,  the  emery , or  cutting  mate- 
rial, and  the  bond,  or  matrix.  The  sharp  points,  or  corners, 
of  the  grains  of  emery  in  the  wheel  constitute  an  indefinite 
number  of  cutting  points  or  edges. 

24.  Bonds  for  Emery  Wheels. — In  order  that  these 
sharp  and  hard  points  may  be  effective  in  cutting  away  the 
material  presented  to  them,  the  grains  must  be  firmly  held, 
just  as  a diamond  point  used  for  cutting  glass  must  have 
a suitable  setting.  The  bond,  or  matrix,  of  the  wheel  fur- 
nishes this  setting  for  the  grains  of  emery.  It  must  be 
strong  enough  to  form  a wheel  that  will  resist  the  centrifu- 
gal force  due  to  the  high  speeds  at  which  the  wheels  must 
be  run  to  secure  their  greatest  efficiency,  and,  also,  must  be 
hard  enough  not  to  wear  away  too  rapidly  and  let  the  grains 
of  emery  loose  before  they  have  done  their  work.  On  the 
other  hand,  the  bond  must  not  be  too  hard,  or  it  will  not 
give  way  when  the  projecting  corners  of  the  grains  of  emery 
have  been  reduced  by  contact  with  the  work,  and  the  wheel 
will  acquire  a hard,  smooth  surface,  with  no  cutting  proper- 
ties. The  character  and  quality  of  the  bond  are,  therefore, 
of  great  importance  in  the  manufacture  of  emery  wheels. 


CLASSIFICATION  OF  EMERY  WHEELS. 

25.  General  Consideration. — -Emery  wheels  may  be 
classified  with  reference  to  the  material  used  for  bond,  the 
principal  varieties  being  as  follows:  (a)  Wheels  with  a vitri- 
fied bond,  known  as  vitrified  wheels ; ( b ) wheels  with  a 


12 


GRINDING. 


18 


silicate-of-soda  bond,  known  as  silicate  wheels ; (c)  wheels 
with  a shellac  bond,  known  as  gum  or  elastic  wheels ; 

( d ) wheels  with  a rubber  bond,  known  as  vulcanite  wheels  ; 

(e)  wheels  with  a celluloid  bond,  known  as  celluloid  wheels ; 

(f)  wheels  with  a preparation  of  leather  bond,  known  as 
tanite  wheels . 

26.  Vitrified  Wheels.  — The  material  used  for  the 
bond  in  vitrified  wheels  is  a mixture  of  certain  clays  and 
fluxes.  When  these  clays  have  been  thoroughly  mixed  with 
the  emery  in  the  proper  proportions,  usually  by  means  of 
water,  the  mass  is  dried  sufficiently  to  allow  of  its  being 
formed  into  a wheel.  This  wheel  is  then  put  upon  a fire- 
brick disk  and  placed  in  a kiln  where  the  temperature  is 
raised  until  the  clay  and  fluxes  begin  to  melt  (probably  about 
3,000°  F.),  so  that  the  whole  wheel  becomes  one  homoge- 
neous mass.  It  is  then  allowed  to  cool,  the  bond  becoming 
essentially  the  nature  of  glass.  This  vitrified  bond,  thickly 
studded  with  grains  of  emery,  is  a vitrified  emery  wheel. 
The  Norton , the  abrasive , the  sterling,  the  Grant , and  the 
safety  are  examples  of  vitrified  wheels. 

27.  Silicate  Wheels. — When  silicate  of  soda  is  used 
as  a bond,  this  material,  after  being  prepared  and  mixed 
with  the  emery,  is  tamped  into  a mold,  and  the  bond  hard- 
ened by  drying  in  an  oven  at  a moderately  low  temperature, 
say  325°  to  400°  F.  The  Detroit  and  the  Scranton  are  exam- 
ples of  silicate  wheels,  though  similar  wheels  are  made  by 
several  other  companies. 

28.  Shellac  Wheels.  — Shellac  wheels  are  made  by 
mixing  the  emery  with  a preparation  of  shellac,  forming  the 
wheels  in  molds,  and  hardening  them  by  heat  at  a low  tem- 
perature, say  from  300°  to  400°  F. 

29.  Vulcanite  Wheels. — In  the  manufacture  of  vul- 
canite wheels,  the  preparation  of  rubber  that  forms  the  bond 
is  filled  with  emery  and  the  mass  made  homogeneous  by 
being  repeatedly  passed  between  rolls.  In  the  case  of  thick 
wheels,  several  sheets,  or  layers,  from  the  rolls  may  be  used 


§18 


GRINDING. 


13 


to  form  a single  wheel.  The  wheel  is  then  subjected  to 
hydraulic  pressure  and  afterwards  placed  in  a vulcanizer, 
where  it  is  exposed  for  some  time  to  a degree  of  tempera- 
ture sufficient  to  harden  the  bond.  When  the  wheel  is  used, 
the  heat  generated  melts  away  the  bond  fast  enough  to 
loosen  and  drop  out  the  kernels  of  emery  as  fast  as  they 
become  dull,  thus  keeping  the  wheel  sharp. 

30.  Celluloid  wheels  are  made  by  but  one  company. 
They  are  strong  and  can,  therefore,  be  run  at  high  speeds. 
Also,  very  thin  wheels  of  this  type  may  be  used  with  safety. 

31.  Tanite  Wheels.- — Tanite  is  a substance  that  was 
invented  and  first  used  for  the  manufacture  of  buttons, 
combs,  and  fancy  articles.  When  it  was  found  to  be  a suit- 
able bond  for  an  emery  wheel,  the  Tanite  Company  became 
known  as  the  manufacturer  of  tanite  emery  wheels.  Tanite 
is  hard  and  strong  at  low  temperatures,  but  soft  and  plastic 
at  high  temperatures.  Hence,  a tanite  wheel  has  somewhat 
of  the  qualities  of  a vulcanite  wheel;  that  is,  when  the  wheel 
is  used  the  heat  softens  the  bond  at  its  surface  and  releases 
the  dull  kernels  of  emery. 


PREPARATION  OF  EMERY  WHEELS. 

32.  Bushing  Emery  Wheels.  — In  ordering  emery 
wheels,  one  of  the  dimensions  that  should  be  given  is  the 
diameter  of  the  spindle  on  which  the  wheel  is  to  run.  The 
wheel  is,  therefore,  made  with  a hole  in  the  center  some- 
what larger  than  the  largest  spindle  that  is  used  to  carry  a 
wheel  of  its  size,  and  when  an  order  is  received,  the  wheel 
is  “ bushed  ” to  the  size  of  spindle  for  which  it  is  ordered. 

The  bushing  is  usually  of  lead.  The  wheel  is  placed  in  a 
horizontal  chuck  with  a bushing  spindle  of  the  required  size 
at  the  center  of  the  chuck,  and  melted  lead  poured  into  the 
annular  space  between  the  bushing  spindle  and  the  wheel. 
As  the  emery  wheel  when  sent  out  must  have  a perfectly 
cylindrical  surface,  it  is  necessary  in  ordinary  methods  of 
truing  that  the  bushing  be  done  before  truing  the  periphery 
of  the  wheel. 


14 


GRINDING. 


§18 


33.  Truing  Emery  Wheels. — Purchasers  of  emery 
wheels  generally  demand  that  the  wheels  be  not  only  round, 
but  of  uniform  thickness.  In  most  processes  of  making 
wheels,  the  shape  of  a wheel  changes  slightly  when  the  bond 
hardens.  Sometimes  the  wheel  warps,  but  it  always  shrinks 
an  uncertain  amount.  It  is  therefore  necessary  that  the 
wheels  be  trued  both  on  their  faces,  to  make  them  of  uni- 
form and  correct  thickness,  and  on  their  peripheries,  to  make 
them  true  cylinders.  Inasmuch  as  the  wheel  is  made  to  cut 
other  substances,  rather  than  to  be  itself  rapidly  reduced  in 
size,  the  truing  is  one  of  the  most  difficult  and  expensive 
processes  involved  in  its  manufacture. 

There  are  two  principal  methods  used  in  truing.  One 
is  to  cut  away  the  material  of  the  wheel  by  means  of  some 
harder  substance  than  the  wheel  itself,  as  the  diamond. 
This  method  is  expensive,  and  is  impracticable  for  large 
and  coarse  wheels.  The  other  method  is  to  use  a dressing 
tool  made  of  steel  or  chilled-iron  disks,  either  flat  or  conical, 
that  are  free  to  revolve  on  a central  spindle.  This  tool  is 
pressed  against  the  revolving  wheel,  and  as  the  disks  of  this 
dressing  tool  revolve  in  rolling  contact  with  the  emery  wheel, 
the  kernels  of  emery  are  dislodged,  the  action  of  the  disks 
of  the  tool  being  somewhat  like  that  of  a quick,  sharp  blow. 

The  action  of  the  disk-dressing  tools  upon  an  emery  wheel 
is  similar  to  that  of  the  stone-cutter’s  point  tool,  or  chisel, 
used  in  dressing  stone;  and  just  as  a chisel,  or  point  tool, 
can  be  made  to  cut  stone  much  harder  than  itself,  so  the 
dressing  tool  can  be  made  to  break  the  projecting  kernels 
out  of  the  rapidly  revolving  emery  wheel,  thus  giving  the 
wheel  an  even  surface. 

34.  The  truing  tool  may  be  used  as  part  of  an  auto- 
matic machine,  or  it  may  be  used  as  a hand  tool.  The 
manufacturer,  in  preparing  wheels  for  the  market,  frequently 
uses  the  automatic  machine.  The  user  of  emery  wheels 
should  have  a hand  dresser,  to  true  the  wheels  whenever 
they  w^ear  a little  out  of  round.  Fig.  4 illustrates  three 
different  kinds  of  hand  tools  for  truing  and  dressing  the 


GRINDING. 


15 


§18 

peripheries  of  wheels,  all  of  which  are  similar  in  their  action. 
They  are  composed  of  a handle  a , carrying  a number  of 


hardened  disks  b , which  may  be  brought  into  contact  with 
the  surface  of  the  emery  wheel.  The  projection  c serves  as 
a support  for  the  tool  when  in  use. 


GRADING  EMERY  WHEELS. 

35.  Emery  wheels  are  graded  by  a process  in  which  the 
hardness  of  the  wheel  relative  to  some  arbitrary  standard  is 
determined.  The  manufacturer  grades  each  wheel  as  closely 
as  possible,  and  publishes  in  his  catalogue  an  explanation  of 
his  system  of  grading.  The  buyer,  in  ordering,  must  either 
know  the  grade  of  wheel  that  will  do  his  special  work,  or  he 
must  describe  the  work  and  allow  the  manufacturer  or 
dealer  to  select  it  for  him.  On  many  kinds  of  work,  a slight 
variation  from  the  correct  grade  will  cause  the  wheel  to 
give  poor  results;  the  very  best  wheel  for  one  kind  of  work 
may  be  useless  for  another  kind  or  quality  of  metal.  The 
user  of  emery  wheels  should,  therefore,  exercise  much  judg- 
ment in  the  selection  of  wheels  in  order  that  they  may  be 
adapted  for  the  purposes  for  which  they  are  to  be  used. 


TABLE  FOR  SELECTION  OF  GRADES, 


1G 


GRINDING.  ' § 18 


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GRINDING. 


17 


§ 18 

36.  Makers  of  vitrified  wheels  use  as  a system  of  des- 
ignating grades,  the  letters  of  the  alphabet,  the  first  letters 
indicating  the  softer  wheels.  To  give  an  idea  of  the  relations 
of  the  grades  to  the  work  to  which  each  grade  is  adapted, 
Table  II,  published  by  The  Norton  Emery  Wheel  Company, 
is  given.  This  table  agrees  quite  closely  with  the  system 
of  grading  that  is  used  by  most  of  the  makers  of  vitrified 
wheels. 

37.  Testing  Emery  Wheels. — Emery  wheels  some- 
times break  or  burst  while  running,  which  accident,  in  the 
case  of  a large  wheel,  is  liable  to  do  considerable  damage, 
besides  endangering  the  life  of  the  workman  using  it.  In 
most  cases  where  a wheel  breaks  when  running,  a careful 
examination  of  the  conditions  reveals  some  adequate  cause 
other  than  the  inherent  weakness  of  the  wheel.  To  be  sure 
that  the  wheel  is  sound  and  strong  when  it  leaves  the  fac- 
tory, the  manufacturer  should  test  it  by  running  it  for  a 
short  time  at  a higher  rate  of  speed  than  will  be  required 
when  the  wheel  is  in  actual  use. 

38.  The  machine  used  for  such  testing  must  have  a 
cover  for  the  wheel  that  will  arrest  the  pieces  if  the  wheel 
should  break.  The  centrifugal  force  acting  to  break  a wheel 
is  proportional  to  the  square  of  the  number  of  revolutions 
made  by  the  wheel;  therefore,  if  the  speed  is  doubled,  the 
centrifugal  force  is  quadrupled.  It  is  customary,  in  testing 
wheels  for  strength,  to  run  them  at  nearly  double  their 
Working  speed,  such  a test  being  almost  sure  to  break  a 
wheel  if  it  is  not  free  from  cracks  or  other  defects. 

39.  The  following  table  shows  the  number  of  revolutions 
per  minute  for  specified  rates  of  periphery  speed,  also  the 
stresses  per  square  inch  on  vitrified  wheels  at  the  specified 
rates  of  speed.  The  usual  working  surface  speed  is  from 
5,000  to  6,000  feet  per  minute;  the  number  of  revolutions 
corresponding  to  these  surface  speeds  are  given  in  the 
table. 


C.  S.  III.— 3 


SPEEDS  OF  GRINDING  WHEELS, 


18  GRINDING.  § 18 


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GRINDING. 


19 


§ 18 

GRINDING. 

40.  Applications  of  Grinding.  — Emery  wheels  are 
used  for  grinding  all  kinds  of  metals;  also  glass,  porcelain, 
rubber,  wood,  and  leather,  including  the  dressing  of  kid 
skins  that  are  used  for  making  gloves.  They  are  made  in  a 
great  variety  of  sizes  that  range  from  the  small  wheel  used 
by  the  dentist  and  weighing  a fraction  of  an  ounce,  to  wheels 

feet  or  more  in  diameter  and  weighing  1,000  pounds. 
They  are  also  made  in  a variety  of  shapes  for  special 
machines  and  work.  Iron  and  steel  castings,  chilled  rolls, 
hollow  ware,  stove  fittings,  plow  points,  car  wheels,  armor 
plate,  tools  for  cutting  metals  and  wood,  and  such  special 
tools  as  cutters,  reamers,  saws,  etc.  ; also  spheres  and  cyl- 
inders for  roller  bearings,  and  the  interior  surfaces  of  cylin- 
ders that  must  be  accurately  formed,  such  as  the  “ Triple  ” 
cylinders  for  the  Westinghouse  air  brake,  are  all  ground 
with  emery  wheels. 

The  grinding  machine  is  used  successfully  on  the  finest 
work  and  also  on  the  coarsest.  A fine  wheel  will  remove 
.00001  of  an  inch  of  material  from  a cylinder,  while  a coarse 
wheel  will  grind  inequalities  from  the  rough  casting  with 
surprising  rapidity  and  apparent  ease.  Many  persons  having 
seen  the  rapidity  with  which  a large  coarse  emery  wheel  will 
remove  irregularities  from  a casting  have  attempted  to 
substitute  emery  wheels  for  the  lathe  tool  for  roughing 
out  work,  but  as  yet  this  method  has  not  been  a success, 
as  it  always  takes  more  power,  and  up  to  the  present  time 
has  cost  more  to  reduce  metal  to  dust  than  to  chips.  By 
the  use  of  very  large,  heavy,  automatic  machines  using 
large  and  heavy  wheels,  it  may  be  possible  to  reduce  the 
labor  and  wheel  costs  so  low  that  it  will  enable  the  grind- 
ing machine  to  remove  large  amounts  of  stock,  not  only 
faster,  but  cheaper  than  it  can  be  done  in  the  lathe. 

41.  Object. — The  processes  of  modern  grinding  maybe 
said  to  have  three  principal  objects  ; viz.  : First , the  re- 
moval, or  cutting  away,  of  stock  from  the  piece  to  be 
ground.  Second,  the  bringing  of  pieces  to  exact  specified 


20 


GRINDING* 


§ 18 


dimensions.  Third , the  production  of  a satisfactory  finish 
upon  the  surfaces  ground. 


42.  Possibilities.  — The  latest  improved  automatic 
grinding  machines  are  demonstrating  that  large  wheels 
driven  on  rigid  machines  and  with  sufficient  power  will,  in 
many  cases  of  cylindrical  grinding,  remove  a considerable 
amount  of  stock  cheaper  than  it  can  be  removed  in  a lathe. 
Grinding  machines  are,  therefore,  likely  to  come  into  more 
general  use,  because  they  can  successfully  compete  with  the 
lathe  where  accurate  work  and  smooth  finish  are  required. 
Indeed,  the  field  for  grinding  by  automatic  machines  has 
recently  been  greatly  enlarged  by  improving  the  design  of 
the  machine  and  using  larger  wheels. 


POLISHING  AND  BUFFING. 


POLISHING. 

43.  Object. — Polishing  differs  from  grinding  in  that  it 
is  not  done  to  remove  material  or  change  the  size  and  shape 
of  the  work,  but  simply  to  create  a bright  or  smooth  surface. 

44.  Polishing  Wheels  and  Belts. — Polishing  wheels 
are  usually  made  by  covering  the  periphery  of  wooden 
wheels  with  leather  and  gluing  to  this  leather  a coating  of 
emery.  This  is  done  by  coating  the  leather  with  hot  glue, 
and  before  the  glue  becomes  dry  rolling  the  wheel  in  loose 
emery  until  -the  emery  ceases  to  adhere  to  it.  When  used, 
such  wheels  are  trued,  in  a sense,  by  holding  an  oilstone  or 
other  hard  substance  against  them  while  they  are  being 
run.  This  levels  the  rough  or  projecting  places. 

Flat  and  curved  surfaces  are  polished  on  the  periphery  of 
wheels  and  more  irregular  objects  are  polished  by  holding 
and  turning  them  against  leather  belts  covered  with  emery 
and  running  over  pulleys,  these  belts  being  wide  or  narrow, 
tight  or  loose,  according  to  the  shape  of  the  work. 


GRINDING. 


21 


§18 


When  polishing,  the  work  is  held 
in  the  hand  and  moved  in  such  a 
manner  that  the  desired 'finish  is 
produced.  Much  practice  is  re- 
quired to  polish  fine  work,  as  it  is 
a matter  of  skill  and  touch  on  the 
part  of  the  workmen. 

45.  Enclosed  Polishing 
Wheel.  — Polishing-wheel  ma- 
chines are  usually  of  a primitive 
nature.  Sometimes  they  are  com- 
posed simply  of  two  uprights  in 
which  are  held  wooden  plugs  hav- 
ing holes  in  their  ends  that  receive 
the  points  of  the  polishing  spindle. 
There  are,  however,  a few  modern 
machines  for  polishing,  one  of  which 


Fig.  5. 

is  illustrated  in  Fig.  5. 
The  interior  of  the 
base  a is  so  formed 
that  the  air-current 
caused  by  the  rotation 
of  the  wheel  when 
running  will  remove 
all  dust  caused  in  pol- 
ishing and  deposit  it 
on  the  floor  behind 
the  machine  or  in  the 
water  tank  c.  The 
wheel  b rotates  in  the 
direction  indicated  by 
the  arrow.  At  the 
back  a shield  d is  so 
arranged  that  it  can 
be  adjusted  to  almost 
touch  the  face  of  the 
wheel.  This  shield 
stops  the  current  of 


22 


GRINDING. 


§18 


air  rotating  with  the  wheel  and  turns  one  current  down- 
wards through  the  passage  ft  while  another  current  passes 
downwards  through  the  passage  gt  but  both  air-currents 
are  discharged  at  the  back  of  the  machine  through  the 
opening  h.  This  machine  was  devised  to  polish  small  work. 
The  wheels  used  in  it  are  covered  with  leather  and  coated 
with  emery. 

46.  Belt  Polishing  Machine. — Fig.  6 illustrates  one 
form  of  mount  for  a polishing  belt.  In  this  case,  a pulley  <2 
has  been  mounted  on  one  end  of  an  ordinary  buffing-wheel 
or  grinding-wheel  arbor.  The  belt  b passes  over  this  pulley 
and  the  outer  end  is  carried  on  the  pulley  c , which  is  sup- 
ported upon  a swinging  arm  d that  is  controlled  by  a 
brace  f.  By  means  of  the  brace  f,  the  tension  on  the  belt  b 
may  be  regulated.  This  belt  is  coated  with  glue  and  emery, 
or  any  other  suitable  polishing  material. 


BUFFING. 

47.  Distinction  Between  Polishing  and  Buffing. 

Sometimes  buffing  and  polishing  are  considered  one  and 
the  same  thing,  but  it  is  well  to  make  a distinction  between 
them  at  the  point  where  the  finish  becomes  grainless. 

48.  Buffing  Wheels. — The  buffed  or  grainless  finish 
is  obtained  by  means  of  soft  wheels.  These  wheels  are 
sometimes  made  of  felt  covered  with  emery,  but  usually  they 
are  formed  of  layers  of  cotton  cloth  that  are  cut  into  round 
blanks  about  12  inches  in  diameter,  which  have  a hole  in  the 
center.  These  round  blanks  are  piled  one  above  the  other 
until  there  are  enough  to  form  a wheel  from  2 to  4 inches 
thick.  These  are  then  placed  on  the  arbor  of  the  machine 
and  bound  together  at  the  center  by  collars  and  a nut.  The 
larger  these  collars  are,  the  harder  will  be  the  wheel  when 
running;  the  smaller  the  collars,  the  softer  will  be  the  wheel 
when  running. 


18 


GRINDING. 


23 


It  should  be  understood  that  when  this  wheel  that  consists 
of  layers  of  cotton  cloth  is  in  place  on  the  arbor  of  the 
machine,  the  edges  of  the  cloth  are  presented  to  the  work, 
or  form  the  periphery  of  the  wheel.  In  use,  this  wheel  is 
revolved  (if  12  inches  in  diameter)  from  4,000  to  G,000  rev- 
olutions per  minute,  according  to  the  practice  of  the  operator 
who  may  be  using  it. 

49.  The  object  of  using  cloth  in  this  manner  is  to  give 
a yielding  wheel  into  the  periphery  of  which  the  operator 
can  press  the  work,  which  usually  is  irregular.  In  this  way 
the  cloth  is  made  to  rub  every  corner  and  curve  of  the  work 
and  the  lines  of  its  motion  are  in  all  directions,  thereby  not 
only  polishing  all  corners  and  curves,  but  also  giving  a 
grainless  surface. 

50.  Cutting  or  Polishing  Material  Used  in  Buff- 
ing.— The  cutting  or  polishing  material  is  used  in  the  form 
of  a cake  that  is  made  by  compressing  tallow,  or  other 
heavy  grease,  together  with  emery,  crocus,  flour  emery, 
rouge,  and  any  other  material  that  may  be  in  vogue  with 
the  particular  operator,  some  using  one  kind  and  some 
another;  the  coarser  material  is  used  for  roughing  and  the 
finer  material  for  finishing  and  “ coloring,  ” as  it  is  known 
in  the  workshop.  This  material  is  applied  to  the  wheel  by 
holding  it  firmly  against  the  edges  of  the  cloth,  as  the  wheel 
revolves,  until  the  edges  become  saturated ; it  is  also  applied 
from  time  to  time  as  the  operator  wishes  to  change  the 
cutting  quality  of  the  wheel. 

51.  Applications  of  Buffing.  — Buffing  is  used  for 
plated  ware  and  for  the  peculiar  surface  that  is  common  on 
bright  vases,  culinary  articles,  and  lacquered  surfaces. 
Much  buffing  is  done  by  first  cutting  down  with  a rough 
material  on  the  wheel,  then  finishing  ready  for  plating.  In 
the  workshop  this  finishing  operation  is  called  coloring. 
In  some  of  the  finer  grades  of  work,  this  is  accomplished  by 
holding  it  against  a very  soft  cotton-cloth  wheel  that  has 
no  cutting  material  upon  it.  If  the  pressure  and  speed  are 


24  GRINDING.  § 18 

suited  to  the  substance  of  which  the  article  is  made,  a very- 
bright  surface  will  be  produced. 

It  is  a well-known  fact  that  with  plated  ware  the  per- 
fection of  the  surface  after  plating  will  never  be  greater 
than  the  surface  on  which  the  plating  is  deposited.  After 
the  article  is  plated,  it  is  again  taken  to  the  soft  buffing 
wheels  and  colored,  which  removes  all  stains  from  the  plating 
bath  and  gives  that  peculiar  luster  that  the  operator  calls 
“ color.” 

Some  work  is  first  polished  and  then  buffed,  but  in  such 
cases  the  material  is  usually  hard,  such  as  steel,  while  brass 
and  softer  metals  are  not  so  treated. 

52.  Buffing-Wheel  Mount. — Fig.  7 illustrates  a light 
buffing-wheel  mount  that  may  also  be  used  for  small  emery 

wheels.  A rag  wheel  is 
shown  on  the  left-hand 
spindle  at  a.  In  the  style 
shown,  the  wheel  is  mount- 
ed on  a bench  stand. 
Similar  wheels  are  built 
that  are  mounted  on  posts 
that  stand  on  the  floor. 
The  machine  is  driven  by 
a belt  that  runs  on  the 
pulley  l \ and  has  provision  for  a second  wheel  at  c. 

53.  Brush  Wheels.  — For  polishing  purposes,  wheels 
are  frequently  made  that  are  surrounded  by  bristle  brushes, 
or  brushes  made  of  other  materials.  In  using  these  wheels, 
the  material  is  applied  to  the  brush  either  in  the  form  of  a 
wash  or  a wax,  as  in  the  case  of  buffing  wheels  or  rag  wheels. 
Brush  wheels  are  more  expensive  than  rag  wheels  and  are 
not  extensively  used  in  machine  shops. 

54.  Leather  Wheels. — Wheels  for  polishing  purposes 
are  frequently  cut  from  leather.  For  very  small  wheels, 
disks  may  be  cut  from  thick  saddle  skirting,  while  when 
larger  disks  are  required  they  are  cut  from  walrus  hide, 


GRINDING. 


25 


§ 18 

which  can  be  obtained  an  inch  or  more  in  thickness  and 
makes  an  excellent  polishing  wheel.  The  polishing  material 
is  usually  mixed  with  oil  or  water,  oil  being  preferred. 


SELECTION  OF  GRINDING  WHEELS. 

55.  General  Remarks.  — When  selecting  grinding 
wheels,  it  is  well  to  understand  that  the  smoothness  of  the 
surface  required  on  the  work  depends  on  other  conditions 
as  well  as  the  size  of  grains  of  which  the  wheel  is  composed. 
A fine-grained  wheel  does  not  produce  a fine  surface  simply 
because  the  wheel  is  fine.  In  fact,  it  may  produce  a very 
coarse  surface,  and  a coarse-grained  wheel  may  produce  a 
fine  surface,  when  of  the  right  grade  and  used  at  a speed 
best  adapting  it  to  the  material  being  ground. 

56.  Grading  of  Grinding  Wheels.  — Emery  and 
corundum  wheels  are  made  in  different  grades  of  hardness, 
and  according  to  the  standards  of  the  Norton  Emery  Wheel 
Company,  the  grade  of  vitrified  wheels  is  denoted  by  letters, 
A being  the  softest.  The  grades  most  commonly  used  are 
J,  K,  L,  M,  N,  O,  P,  and  Q.  The  grades  of  elastic  or  gum 
wheels  are  denoted  by  numbers,  which  range  from  0 to  6, 
each  number  being  ^ larger  than  the  preceding  one;  viz., 
0,  i,  f,  1,  etc.  Numbers  1 to  5 are  those  most  commonly 
used. 

Other  companies  have  other  systems  of  grading.  Some 
grade  their  wheels  from  A to  Z,  A being  extremely  soft  and 
Z extremely  hard.  The  Carborundum  Company  grade 
their  wheels  from  D to  Y,  D being  hard  and  V being 
very  soft.  * 

57.  Relation  Between  Grade  of  Wheel  and 
Work,  — Hard-grade  wheels  retain  their  particles  longer 
than  softer  ones;  therefore,  the  softer  grades  are  said  to 
cut  sharp , because  the  particles  are  torn  out  by  the  act  of 
grinding  before  they  become  dull,  and  thus  new  ones  are 
constantly  being  exposed  to  the  work.  Some  kinds  of  work 


26 


GRINDING. 


§ 18 

require  that  these  particles  shall  be  torn  out  before  they 
become  at  all  dull,  while  other  kinds  of  work  require  that 
they  shall  be  retained  until  they  become  quite  dull  and 
smooth.  Between  these  extremes,  there  is  a great  variety 
of  work  that  requires  a variety  of  grades  of  wheels. 

Different  materials  and  different  shapes  of  work  require 
different  sizes  of  grain  combined  with  different  bonds  and 
grades  of  hardness.  In  general,  the  harder  that  the  mate- 
rial to  be  ground  is,  the  softer  must  the  wheel  be,  and  the 
coarser  may  it  be.  With  steel,  the  hardness  of  the  wheel 
varies  inversely  with  the  softness  of  the  material  that  is  to 
be  ground.  Brass,  copper,  and  rubber  require  soft  wheels, 
and  rubber  very  coarse  ones.  Hardened  steel,  cast  iron, 
and  chilled  iron  require  soft  wheels  in  order  that  the  parti- 
cles of  emery  and  corundum  may  be  broken  out  as  they  be- 
come dull  and  thus  constantly  present  new  ones  to  the 
work.  Brass,  copper,  and  rubber  require  soft  wheels  in 
order  that  the  material  being  ground  may  not  adhere  to  the 
wheel,  but  that  the  particles  of  emery  may  be  torn  out  be- 
fore the  brass  or  copper  can  adhere.  Soft  steel  requires  a 
harder  wheel  than  hardened  steel,  because  the  particles  of 
emery  are  not  dulled  so  soon  and,  entering  deeper  into  the 
work,  are  torn  out  more  readily.  Hardened  steel,  cast  iron, 
and  chilled  iron  require  soft  wheels  because  these  materials 
dull  the  particles  of  emery  and  corundum  very  quickly, 
making  it  necessary  to  throw  them  away  rapidly. 

58.  Glazing. — When  grinding  hardened  steel  with  a 
wheel  that  is  too  hard,  the  wheel  will  be  worn  bright  and 
smooth  and  will  cut  but  little.  This  is  known  as  glazing. 
When  soft  steel  is  ground  with  a wheel  that  is  too  hard  for 
the  work,  the  wheel  will  fill  with  steel;  for,  since  the  parti- 
cles remain  sharp  and  enter  deep  into  the  soft  steel,  they 
cause  the  steel  to  adhere  to  them,  especially  if  there  is  con- 
siderable pressure  on  the  wheel.  Fine-grained  wheels  when 
hard  fill  and  glaze  sooner  than  coarse  ones  of  the  same 
grade;  and,  when  soft,  wear  away  faster  than  coarse  ones 
of  the  same  grade  when  cutting  the  same  depth. 


GRINDING. 


27 


§ 18 

HAND  GRINDING. 

50.  General  Consideration.  — The  term  liand 
grinding  is  generally  understood  to  cover  those  operations 
in  which  the  work  is  held  by  liand,  pressed  against  the 
emery  wheel,  and  moved  about  either  with  or  without  the 
aid  of  a rest.  There  is  a class  of  machines  in  which  the  work 
is  large  and  stands  still,  while  the  emery  wheel,  which  is 
mounted  in  a swinging  frame,  is  moved  about  so  as  to  grind 
the  surface  of  the  work. 

GO.  Simple  Hand  Grinding  Machine. — The  grind- 
ing machine  used  in  foundries  for  smoothing  castings,  and 
which  is  illustrated  in  Fig.  8,  is  perhaps  the  most  common 
type  of  a hand  grinding  machine.  These  machines  are  made 
in  a great  variety  of  sizes,  carrying  wheels  from  3 inches  to 
3G  inches  in  diameter.  The  style  shown  is  provided  with 


fig.  8. 


rests  a upon  which  the  work  may  be  placed  while  it  is  being 
ground.  For  truing  emery  wheels,  truing  devices  are  per- 
manently attached  to  the  machine  and  shown  below  the 
rests,  € being  the  axis  on  which  the  device  works,  d the 
truing  wheel,  and  b the  handle  by  means  of  which  it  is  con- 
trolled. Whenever  the  wheel  gets  out  of  true,  the  truing 
device  can  be  brought  into  contact  with  the  face  of  the 


28 


GRINDING. 


§18 


wheel  and  moved  across  the  face  on  the  axis  c,  thus  quickly 
truing  the  surface  of  the  wheel  e.  The  wheels  e are  driven 
by  means  of  a belt  on  the  pulley  f. 

In  some  cases,  similar  machines  are  used  where  consider- 
able skill  is  required  to  produce  the  work,  but  as  a rule  this 
type  is  used  only  for  comparatively  rough  work. 


MACHINES  EMPLOYING  EMERY  WHEELS. 

61.  Table  Machine.  — The  machine  illustrated  in 
Fig.  8 is  intended  for  rough  work.  Where  approximately 


bearing  for  the  shaft  being  carried  by  the  bracket  c.  Above 
the  emery  wheel  is  mounted  a table  e through  which  the 
upper  face  of  the  wheel  projects.  As  shown  in  the  illustra- 
tion, the  table  is  provided  with  an  adjustable  fence  f for 
guiding  the  work  on  the  surface.  The  table  e can  be  ad- 
justed by  means  of  the  screw  shown  at  the  front  of  the 
table,  to  make  allowance  for  wear  in  the  emery  wheel  or  to 
adjust  the  depth  of  cut  taken.  This  machine  will  produce 
approximate  flat  surfaces  and  is  very  useful  for  removing 


HAND  SURFACING  MACHINES. 


flat  surfaces  are  required 
without  special  regard 


3 being  paid  to  the  angles 
between  the  faces,  a ma- 
chine of  the  class  illus- 
trated in  Fig.  9 may  be 


Fig.  9. 


b employed.  The  illustra- 
tion shows  one  bearing 
and  one  emery  wheel  of 
a machine  provided  with 
a surfacing  table.  The 
emery  wheel  a is  mounted 
on  a shaft  b driven  by  a 
belt  on  the  pulley  d , one 


GRINDING. 


29 


§ 18 

rough  parts  from  flat  surfaces,  but  is  not  especially  adapted 
for  producing  correct  angles.  The  machine  is  limited  to 
work  of  such  a size  that  can  be  easily  handled  and  placed 
upon  the  table. 

62.  Swinging-Frame  Machine. — Where  large  work 
is  to  be  ground  or  polished,  as,  for  instance,  portions  of 
engine-frame  castings  and  cylinders,  and  similar  work 
that  frequently  requires  finishing,  and  where  the  work  is  of 
such  great  size  that  it  would  be  impossible  to  take  it  to  the 
emery  wheel,  a machine  of  the  class  illustrated  in  Fig.  10 


may  be  employed.  This  machine  consists  of  a bracket  a 
fastened  to  the  ceiling  that  carries  the  countershaft  on  which 
are  placed  tight  and  loose  pulleys  b and  the  pulleys  c.  This 
countershaft  is  driven  by  a belt  on  the  pulley  by  while  the 
emery  wheel  is  driven  by  a belt  on  the  pulley  c,  which  drives 
the  pulley  e,  which  is  permanently  attached  to  the  pulley  f 
The  belt  on  the  pulley  /"drives  a pulley  on  the  emery-wheel 


30 


GRINDING. 


18 


shaft,  thus  imparting  power  to  the  emery  wheel  h.  The 
swinging  frame  d is  supported  from  the  countershaft  bear- 
ings and  the  swinging  frames  is  counterbalanced  by  means 
of  a weight  m and  a suitable  rope  passing  over  the  pulleys, 
as  shown.  The  emery  wheel  h is  mounted  on  a shaft  at  the 
end  of  the  swinging  frame  g and  is  provided  with  a yoke  / 
and  handles  i and./f,  by  means  of  which  its  motion  can  be 
controlled.  The  connecting  portion  n below  the  swinging 
frame  d is  so  arranged  that  it  can  swivel  in  the  frame  d , and 
the  portion  connecting  the  swinging  frame  g with  the  shaft 
carrying  the  pulleys  e and  f is  also  arranged  so  that  it  can 
swivel.  The  result  is  that  the  emery  wheel  h can  be  turned 
to  any  angle  or  into  almost  any  plane,  either  horizontal  or 
vertical.  This  enables  the  operator  to  grind  both  surfaces 
and  edges  of  the  work,  or  to  round  corners.  This  class  of 
machine  has  found  a great  field  of  usefulness,  especially  in 
the  finishing  departments  of  shops  producing  rather  large 
work,  but  considerable  skill  on  the  part  of  the  operator  is 
required  to  produce  a smooth  surface  with  it. 

63.  Upright  Surface  Grinding.  — Flat  work  may 
also  be  ground  by  holding  it  against  the  side  of  an  emery 
wheel  similar  to  that  shown  in  Fig.  8,  but  this  is  rather  an 
awkward  and  difficult  method  of  procedure  and,  hence, 
emery  wheels  have  been  mounted  on  vertical  axes  so  that 
the  work  may  be  placed  on  the  side  of  the  wheel  and  thus 
ground  flat.  Such  machines  are  called  upright  surface 
grinders  and  are  used  to  a considerable  extent  on  some 
classes  of  work. 


DISK  GRINDERS. 

64.  All  machines  using  emery  wheels  have  the  com- 
mon disadvantage  that  it  is  difficult  to  keep  the  surface  of 
the  emery  wheel  true;  hence,  accurate  work  cannot  be  pro- 
duced by  this  class  of  hand  grinding  machines  without 
placing  the  machines  under  special  runners  and  providing 
truing  devices  for  the  wheels.  To  overcome  this  difficulty, 
the  disk  surface  grinders  have  been  brought  out.  A 


GRINDING. 


31 


§18 


type  of  disk  surface  grinder  is  illustrated  in  Fig.  11.  The 
grinding  is  done  by  means  of  emery  cloth  secured  to  the 
steel  disks  a.  These 
disks  are  from  inch 
to  j-  inch  thick,  are 
ground  perfectly  true 
and  parallel,  and  are 
provided  with  a spiral 
groove  on  the  side 
running  from  the  cen- 
ter to  the  periphery. 

Emery  cloth  is  then 
glued  or  cemented  up- 
on each  side  of  these 
disks.  In  cementing 
the  emery  cloth  on, 
it  is  pressed  firmly 
against  the  disk  so  as 
to  bed  it  into  the 
groove.  This  provides  a space  into  which  any  particles  of 
emery  or  grinding  dust  will  pass  and  so  prevent  them  from 
scoring  the  surface  of  the  work. 

The  disks  are  used  until  one  side  is  dull  and  are  then  re- 
versed and  used  until  the  other  side  is  dull,  when  they  are 
replaced  by  other  disks  and  the  worn  ones  recovered.  The 
machine  shown  illustrates  two  principles  of  grinding  that 
may  be  employed.  At  the  left-hand  side  of  the  machine  there 
is  a simple  flat  table  b whose  upper  surface  is  scraped  at 
exactly  right  angles  to  the  disk;  by  holding  any  flat  surface 
upon  this  table,  a surface  at  exactly  right  angles  to  it  can 
be  ground  by  the  disk. 


fig.  li. 


65.  The  manufacturers  claim  that  it  is  easily  possible  to 
grind  small  work  within  the  limit  of  .001  inch  on  these  ma- 
chines. When  it  is  desired  to  grind  at  any  other  angle  than 
a right  angle,  an  attachment  similar  to  that  shown  at  the 
right-hand  side  of  the  illustration  may  be  used.  This  is 
provided  with  a graduated  circle  on  the  piece  c by  means  of 


32 


GRINDING. 


§18 

which  the  table  can  be  set  at  any  angle  to  the  disk.  It  is 
also  provided  with  a sliding  guide  d controlled  by  the  han- 
dle f which  operates  the  feed-screw.  By  providing  a stop 
or  indicator  disk  upon  the  handle  f,  the  exact  thickness  to 
which  the  work  is  ground  can  be  gauged  within  .001  of  an 
inch;  and  by  means  of  the  graduated  circle  on  the  piece  c , 
the  angle  between  the  faces  can  be  accurately  determined. 
This  head  is  also  provided  with  a balance  weight  g by  means 
of  which  it  can  be  arranged  to  oscillate  within  limits,  thus 
swinging  the  work  back  and  forth  across  the  face  of  the 
grinding  disk  and  so  reducing  the  liability  of  producing 
scratches  upon  the  surface.  The  disks  are  carried  upon  the 
shaft  h driven  by  the  pulley  i.  The  machine  is  mounted 
upon  a substantial  base,  provided  with  a cupboard  for  con- 
taining the  grinding  disks. 

The  disk  grinding  machine  does  not  replace  any  particular 
machine  tool  in  the  shop  as  much  as  it  serves  to  do  work 
that  is  ordinarily  done  by  filing,  but  it  will  be  found  possible 
to  do  a large  amount  of  work  that  is  ordinarily  done  at  the 
bench  on  a machine  of  this  class. 


TOOL  GRINDING. 


HAND  TOOL  GRINDING. 

06.  General  Consideration. — Under  the  heading  of 
hand  grinding  may  be  classed  the  grinding  of  tools  for  turn- 
ing and  planing  metal.  A number  of  different  machines  are 
made  for  this  purpose  on  which  emery  wheels  are  used ; 
some  of  these  grind  dry  and  some  wet.  The  wet  grinding 
wheels  may  be  divided  into  two  classes,  those  that  receive 
their  water  from  the  pump  system  and  those  in  which  the 
wheel  runs  in  a trough  or  bath  into  which  water  may  be 
admitted.  The  dry  grinding  machines  are  comparatively 
little  used  for  tool  grinding,  because  they  are  liable  to  draw 
the  temper  of  tools;  hence,  only  the  wet  grinding  machines 
will  be  described. 


GRINDING. 


33 


§ is 

WET  GRINDING  MACHINE. 

67.  Methods  of  Supplying  Water. — A representa- 
tive tool-grinding  machine  intended  for  wet  grinding  is 
illustrated  in  Fig.  12.  This  machine  is  shown  because  it  is 
arranged  to  provide  for  a supply  of  water  without  the  use 
of  pumps  or  pipes,  and,  also,  because  it  has  a truing  device 
arranged  in  a wheel  guard.  In  Fig.  12  a section  of  the 


machine  is  illustrated,  showing  the  manner  in  which  the 
water  is  applied.  The  water  tank  d is  filled  with  water 
while  the  water  trough  a is  raised  to  its  highest  level  by 
means  of  the  screw  b and  the  lever  c,  this  water  trough  be- 
ing pivoted  at  one  end.  The  water  trough  a surrounds  the 
lower  part  of  the  emery  wheel  and  when  in  its  highest  position 

C.  IIL—4 


34 


GRINDING. 


, § 18 

prevents  water  from  wetting  the  wheel;  as  the  trough  a or 
its  forward  end  is  lowered,  it  sinks  into  the  surrounding 
water  and  allows  it  to  flow  in  around  the  wheel.  The 
trough  is  lowered  sufficiently  to  obtain  the  amount  of  water 
desired  by  the  operator;  the  wheel  throws  the  water  out  at 
the  rear,  but  an  equal  amount,  of  course,  runs  in  at  the 
forward  end  of  the  trough,  thus  keeping  the  supply  con- 
stant. 

68.  Truing  Device. — The  truing  device  consists  sim- 
ply of  a thread  roll  h mounted  on  the  end  of  a rocking 
lever,  so  that  the  operator  can  force  it  against  the  revolv- 
ing wheel  by  means  of  the  screw  f.  This  truing  device  is 
always  ready  for  use. 

69.  Tool  Rest. — The  tool  rest  and  guard  in  this  style  of 
machine  are  shown  at  i and  e . This  rest  is  surrounded  by  a 
guard  e so  arranged  with  a balance  weight  that  it  normally 
occupies  the  position  shown.  When  the  operator  wishes  to 
grind  a tool,  he  places  it  on  the  point  g and  presses  it  down- 
wards until  the  tool  comes  in  contact  with  the  rest  i.  When 
the  grinding  is  being  done,  the  guard  rises  and  prevents 
water  from  spattering  out  in  front,  no  matter  how  large  an 
amount  of  water  may  be  supplied  to  the  wheel. 


MACHINE  TOOL  GRINDING. 


TYPE  OF  MACHINES. 

70.  General  Consideration. — With  the  growth  of 
machine  manufacturing,  replacing  as  it  does  the  older 
method  of  machine  making,  it  has  become  the  practice  in 
large  machinery  establishments  to  manufacture  the  lathe 
and  planer  cutting  tools  in  large  lots^  These  tools  are  all 
ground  to  the  correct  shapes  and  are  ready  for  the  work- 
man to  use.  The  old  ones  are  reground  and  sharpened  to 
the  standard  forms  and  then  placed  in  the  tool  room,  where 
they  may  at  any  time  be  obtained  by  the  workman. 


GRINDING. 


35 


§18 

The  shapes  of  the  tools  vary  in  different  establishments, 
but  usually  each  establishment  fixes  on  standard  shapes  for 
all  their  cutting  tools  and  the  operator  follows  the  blue- 
print of  standards  that  is  generally  placed  on  the  holders 
shown  at  the  right  of  the  machine  in  Fig.  13. 

This  matter  of  machine  tool  grinding  has  become  of  so 
much  importance  in  the  economy  of  cutting  tools  that  it 
may  be  dignified  as  a trade,  requiring  (as  relating  to  the 
establishment  of  standards  and  the  grinding  of  these  tools 
commercially)  considerable  study  and  care.  It  is  probable 
that  within  a few  years  operators  who  are  skilled  in  the  art 
of  tool  shaping  and  grinding  as  related  to  the  economy  of 
cutting  metal  will  be  in  demand. 

There  are  two  general  classes  of  machines  employed  for 
this  purpose,  one  of  which  uses  an  ordinary  emery  wheel 
and  grinds  the  tools  on  the  face  of  the  emery  wheel,  while 
the  other  employs  a disk  wheel  and  grinds  the  tools  on  the 
flat  face  of  the  disk.  The  machine  manufactured  by 
Wm.  Sellers  & Company,  Philadelphia,  is  a good  repre- 
sentative of  the  first  class,  and  that  manufactured  by  the 
Gisholt  Machine  Company,  Madison,  Wisconsin,  is  a good 
representative  of  the  second  class. 

71.  Sellers  Grinding  Machine. — The  Sellers  ma- 
chine shown  in  Fig.  13  is  called  a universal  tool-grinding 
and  shaping  machine.  This  machine  is  so  constructed  that, 
with  its  fixtures  and  attachments,  the  accuracy  of  the  form 
to  be  ground  is  not  dependent  on  the  skill  of  the  operator, 
but  is  obtained  by  placing  the  various  holders  and  attach- 
ments at  the  angles  required,  these  being  graduated  and 
marked  so  that  if  the  operator  places  them  at  the  right 
graduation  and  angles,  the  accuracy  of  the  grinding  will  be 
insured.  When  the  tools  are  placed  in  the  various  holders, 
the  operator  moves  them  against  the  wheel  by  the  use  of  a 
lever  shown  at  a,  Fig.  13.  Water  is  supplied  to  the  emery 
wheel  by  means  of  a rotary  pump,  and  on  one  side  of  the 
machine  is  attached  a diagram  of  instructions  for  obtaining 
the  standard  shapes.  This  diagram  is  shown  at  b,  Fig.  13. 


36 


GRINDING. 


§18 


The  Sellers  machine  is  designed  to  present  a line  contact 
between  the  emery  wheel  and  the  work  being  ground.  The 
makers  believe  that  it  is  absolutely  necessary,  in  order  to 
efficiently  grind  steel  tools  by  means  of  rapidly  cutting 
wheels,  that  the  contact  between  the  two  should  be  a line 


and  not  a surface;  hence,  if  it  is  desired  to  grind  a plain 
face  of  a tool,  the  wheel  must  have  a cylindrical  or  conical 
surface  past  which  the  surface  to  be  ground  must  be  moved 
in  a plane.  They  further  state  that  the  plane  face  of  the 
wheel  cannot  be  used  for  this  purpose  because  it  and  the 


GRINDING. 


37 


§ 18 

surface  being  ground  will  soon  coincide,  with  the  result  that 
no  cutting  will  be  done,  though  considerable  heat  will  be 
produced. 

72.  The  style  of  Sellers  tool-grinding  machine  shown 
in  Fig.  13  is  provided  with  a conical  wheel  c and  the  tools 
are  held  in  a suitable  fixture  d , one  tool  being  shown  at  e. 
Another  style  of  machine  manufactured  by  the  Sellers  Com- 
pany is  arranged  to  pass  the  work  across  the  periphery  of 
an  ordinary  cylindrical  emery  wheel. 

The  Sellers  machine  will  not  only  grind  all  angles  and 
circles  with  cone  clearance,  but  it  will  also,  by  the  use  of 
forms,  grind  irregularly  shaped  cutting  tools.  On  this 
account,  it  probably  has  a greater  range  than  any  other 
machine  on  the  market  and  is  remarkably  well  adapted  for 
shops  having  a large  variety  of  tools. 

73.  Gisliolt  Tool-Grinding  Machine. — This  ma- 
chine works  on  an  entirely  different  principle  from  the 
Sellers  and  is  intended  only  for  grinding  the  regular  angles 
and  circles  with  clearance.  For  this  reason,  the  Gisholt 
machine  will  not  serve  where  an  extremely  large  range  of 
tools  is  required.  As  in  the  Sellers  machine,  the  accuracy 
of  the  shape  of  the  tool  does  not  depend  on  the  skill  of  the 
workman,  but  is  obtained  by  the  different  angles  at  which 
the  parts  and  various  holders  and  fixtures  are  set,  these 
angles  being  read  from  a chart.  Water  is  supplied  to  the 
wheel  on  this  machine  by  means  of  a pump,  as  in  the  Sellers. 

The  main  point  of  difference  between  the  two  machines  is 
in  the  method  of  presenting  the  work  to  the  wheel.  The 
Gisholt  machine  is  illustrated  in  Fig.  14,  where  it  will  be 
seen  that  the  grinding  is  done  on  the  face  of  a cup-shaped 
wheel,  the  contact  between  the  tool  and  the  wheel  being 
a surface  and  not  a line  contact,  as  the  wheel  and  the  sur- 
face being  ground  coincide.  In  actual  practice,  the  grinding 
is  done  rapidly  without  heating  when  the  right  grade  and 
grain  of  wheel  are  used  and  the  work  is  moved  past  the 
wheel  in  the  right  manner  to  accomplish  the  desired  results. 


38 


GRINDING. 


§18 


In  this  respect  both  machines  are  successful.  The  reason 
for  the  success  of  this  style  of  machine  will  be  shown  under 
the  heading  “ Selection  of  Wheels  for  Tool  Grinding.”  The 
depth  of  cut  is  regulated  by  means  of  a cross-feed  controlled 


Fig.  14. 


by  a hand  wheel  b and  the  tool  is  carried  back  and  forth 
across  the  face  of  the  wheel  by  means  of  the  lever  c.  The 
Gisholt  machine  is  very  simple  and  compact,  as  wdll  be  seen 
by  the  illustration. 


SELECTION  OF  WHEELS  FOR  TOOL  GRINDING. 

74.  Grade  of  Wheel. — In  selecting  wheels  for  tool 
grinding,  as  has  been  stated  where  the  subject  was  under 
discussion,  it  should  be  understood  that  the  result  to  be 


GRINDING. 


39 


§ is 

obtained  is  dependent  on  many  conditions  in  the  wheel 
aside  from  the  size  of  grain.  The  grade  of  the  wheel  plays 
a very  important  part  in  the  manner  in  which  it  does  its 
work.  A good  illustration  in  this  connection  is  the  case  of 
the  Gisholt  and  Sellers  tool-grinding  machines,  which  are 
designed  to  use  diametrically  opposite  methods,  one  using  a 
line  contact  only,  to  avoid  heating  and  glazing,  the  other 
using  a surface  contact,  and  also  avoiding  heating  and 
glazing. 

75.  In  the  case  of  the  Gisholt  machine,  by  using  a cup- 
shaped wheel  and  grinding  against  its  flat  surface,  advan- 
tage is  taken  of  the  possibilities  of  proper  grading  as 
related  to  the  work  in  hand;  for  it  is  true  that  as  the 
surface  in  contact  becomes  greater,  the  grade  of  the  wheel 
should  become  softer,  and  may  be  much  coarser.  In  the 
case  of  the  Sellers  machine,  by  using  a line  contact  on  the 
periphery  or  conical  portion  of  the  wheel,  the  wheel  can  be 
very  much  harder,  which  would  be  an  advantage  if  the 
operator  was  grinding  tools  of  irregular  form  and  wished  to 
preserve  the  shape  of  the  wheel  as  long  as  possible.  This  is 
true  also  in  many  cases  where  it  is  desirable  to  have  the 
wheel  remain  intact,  without  change  of  form  on  the  face. 
The  Gisholt  machine  is  designed  to  grind  flat  surfaces, 
which  are  passed  entirely  across  the  face  of  the  wheel 
at  each  stroke  of  the  lever;  hence,  the  face  of  the  wheel  is 
maintained  in  correct  form  and  the  desired  ^result  is  ob- 
tained. At  the  same  time,  on  the  Gisholt  machine  the 
wheel  may  be  soft  enough  and  coarse  enough  to  cut 
freely. 


76.  The  emery  wheel  for  tool  grinding  should  be  soft 
enough  to  cut  freely  without  requiring  too  great  pressure 
and  without  glazing.  If  only  very  large  tools  that  present 
broad  surfaces  to  the  wheel  are  to  be  ground,  the  wheel 
should  be  softer  than  if  only  those  tools  presenting  very 
small  surfaces  are  to  be  passed  over  it.  The  exact  number 
of  emery  and  the  grade  of  wheel  to  be  used  in  all  cases 


40 


GRINDING. 


§ IB 

cannot  be  given,  because  conditions  vary  so  much.  It  is 
safe  to  assume  that  wheels  for  this  purpose  should  be  so 
made  that  the  desired  surface  on  the  tool  will  be  dependent 
on  the  grade  of  the  wheel  rather  than  the  grain;,  that  is,  the 
wheels  should  be  quite  coarse  and  very  porous,  for,  as  has 
been  stated  before,  a coarse  wheel  will  produce  quite  a fine 
finish  if  of  the  right  grade  and  run  at  the  right  speed  for  the 
work  in  hand. 

77.  Some  workmen  prefer  to  use  a coarse  wheel  for 
shaping  the  tool,  and  a much  finer  one,  quite  soft,  for  a 
slight  cut  to  give  the  desired  surface  for  a cutting  edge. 
In  most  cases,  however,  only  one  wheel  is  necessary,  pro- 
vided the  workmen  use  an  oilstone  for  the  finishing  touch. 

78.  The  tendency  among  users  of  tool  grinders  is  to 
select  wheels  much  too  hard  for  the  purpose.  This  is  owing 
to  the  fact  that  workmen  almost  universally  fail  to  appre- 
ciate the  emery  wheel,  and  do  not  understand  how  light  a 
touch  is  required  to  grind  work  very  rapidly  on  a good 
wheel.  A soft  wheel,  suitable  for  grinding  tools  rapidly, 
will  remove  a large  amount  of  material  instantly  with  a 
very  light  touch  of  the  tool  upon  it.  But  as  workmen  have 
invariably  acquired  their  experience  by  using  grindstones, 
they  nearly  always  bear  hard  upon  the  emery  wheel  when 
grinding  tools.  This  will  wear  a good  wheel  very  rapidly 
and  cut  holes  at  intervals  in  the  periphery.  Thus  it  is  that 
the  purchasers  of  emery  wheels  for  machinery  establishments 
must  select  harder  wheels  than  is  necessary  in  order  to 
preserve  them. 

It  is  a common  complaint  among  manufacturers  of  tool 
grinders  that  they  are  obliged  to  send  out  wheels  that  are 
much  harder  than  the  purpose  requires.  The  three  wheels 
that  are  used  quite  commonly  in  tool  grinders  are  the 
following:  Size  of  grain,  No.  30,  grade  O;  size  of  grain, 
No.  36,  grade  N ; size  of  grain,  No.  45,  grade  N ; all  of  them 
being  designated  by  the  Norton  Emery  Wheel  Company’s 
standard. 


GRINDING. 


41 


18 


MACHINE  GRINDING. 

79.  General  Consideration. — Machine  grinding  may 
be  defined  as  the  art  of  producing  very  accurate  plane, 
cylindrical,  and  conical  surfaces  by  an  abrading  process 
performed  in  an  automatic  grinding  machine.  Machine 
grinding  differs  essentially  from  hand  grinding  in  that  the 
accuracy  of  the  surfaces  produced  by  it  is  dependent  almost 
entirely  on  the  accuracy  of  the  machine  in  which  the  grind- 
ing is  done,  instead  of  on  the  skill  of  the  workman. 

In  the  early  attempts  that  were  made  to  produce  very 
accurate  plane,  cylindrical,  and  conical  surfaces,  a common 
emery  wheel  was  mounted  on  a metal  planer  or  on  a lathe; 
in  fact,  the  first  forms  of  grinding  machines  for  cylindrical 
and  conical  work  were  called  grinding  latlies.  The  early 
attempts  were  far  from  satisfactory,  and  many  persons  sup- 
posed that  the  errors  frequently  found  in  the  work  were  inher- 
ent to  the  grinding  process,  and  could  not  be  eliminated;  in 
other  words,  it  was  supposed  that  grinding  was  incapable  of 
producing  true  work.  Painstaking  experiments  and  a careful 
study  of  the  conditions  convinced  the  pioneer  advocates  of 
machine  grinding  that  the  faulty  work  produced  was  par- 
tially due  to  the  selection  of  wheels  illy  adapted  to  the  work 
expected  of  them,  and  chiefly  to  defects  inherent  to  the 
machinery  used.  The  machinery  was  gradually  improved 
and  the  defects  were  overcome;  and  with  wheels  selected 
to  suit  the  work,  the  grinding  machine  of  today  can  be 
truthfully  said  to  produce  round  work  as  accurate  as  can 
reasonably  be  expected  and  was  ever  hoped  for;  in  addition 
to  this  it  was  found  that  some  lines  of  work  could  be  finished 
to  exact  size  in  much  less  time  than  by  any  other  method. 

80.  Classification  of  Macliine-Grinding  Opera- 
tions.— The  different  grinding  operations  for  which  a 
grinding  machine  is  used  may  be  classified  according  to  the 
position  of  the  surface  operated  on  as  external  grinding  and 
internal  grinding ; or  they  may  be  classified  according  to 
the  character  of  the  surface  as  surface  grinding , which 


42 


GRINDING. 


§18 


term  is  commonly  understood  to  be  an  abbreviation  for 
“plane  surface”  grinding,  cylindrical  grinding,  and  conical 
grinding. 

81.  External  grinding  may  be  defined  as  a grinding 
operation  performed  on  the  outside  surface  of  a solid;  in- 
ternal grinding,  as  the  grinding  of  the  inside  surface  of 
a hole.  The  term  surface  grinding  is  almost  invariably 
understood  to  denote  the  grinding  of  a plane  surface  in  a 
machine  where  the  work  reciprocates  in  a straight  line, 
while  the  term  radial  grinding  or  disk  grinding  is 
applied  to  the  grinding  of  plane  surfaces  on  work  rotating 
about  its  axis.  Cylindrical  grinding,  as  implied  by  the 
name,  denotes  the  grinding  of  a cylindrical  surface,  which 
may  be  the  inside  or  the  outside  surface  of  a solid.  Conical 
grinding  is  a term  that  refers  to  the  grinding  of  a tapering 
solid  of  revolution,  by  solid  of  revolution  being  meant  a 
solid  generated  by  the  revolution  of  some  plane  figure  about 
a line  as  an  axis.  Thus,  a cylinder  is  a solid  of  revolution 
generated  by  revolving  a rectangle  about  one  of  its  sides  as 
an  axis;  a right  cone  is  generated  by  the  revolution  of  a 
triangle  about  one  of  its  sides,  etc. 


GRINDING  SOLIDS  OF  REVOLUTION. 

82.  Governing  Conditions. — The  fundamental  prin- 
ciple underlying  the  grinding  of  solids  of  revolution  is  the 
application  of  thousands  of  cutting  points  to  the  surface  of 
the  work  while  it  is  being  slowly  revolved  about  its  axis. 
Each  cutting  point  removes  an  exceedingly  small  amount 
of  metal;  consequently,  the  pressure  due  to  the  cutting 
operation  is  very  light.  It  follows,  therefore,  that  the  dis- 
turbance of  the  axes  of  the  work  and  the  wheel  is  corre- 
spondingly small,  owing  to  which  fact  the  resulting  solid  of 
revolution  is  exceedingly  true. 

If  the  grinding  wheel  is  traversed  along  the  surface  of  the 
revolving  solid  in  a straight  line  parallel  to  the  axis  of  rota- 
tion of  the  solid,  the  latter  will  be  ground  truly  cylindrical; 


GRINDING. 


43 


§ 18 


but  if  the  line  of  motion  of  the  wheel  is  at  an  angle  to  the 
axis  of  rotation  of  the  solid,  the  latter  will  be  ground  conical. 
It  is  obvious  that  the  grinding  wheel  may  remain  stationary, 
and  that  the  work  may  be  traversed  past  it  without  affecting 
the  result. 

In  practice,  the  work  or  the  wheel  is  made  to  travel  in  a 
straight  line  by  mounting  either  one  on  a carriage  that 
slides  on  straight  guiding  ways  that  are  so  designed  as  to 
resist  wear,  and  so  protected  against  injury  as  to  remain 
true  as  long  as  the  whole  machine  can  reasonably  be  ex- 
pected to  last  without  overhauling  and  repair.  When 
grinding  conical  work,  it  is  absolutely  necessary  that  the 
cutting  be  done  along  a line  lying  in  the  plane  containing 
the  axes  of  the  wheel  and  work,  or,  as  commonly  expressed, 
the  wheel  and  work  must  be  at  the  same  height  above  the 
ways. 


83.  Classes  of  Machines  Used. — There  are  two  gen- 
eral classes  of  grinding  machines,  which  are  called  plain 
grinding  machines  and  universal  grinding  machines.  The 
plain  grinding  machines  are  designed  especially  for 
manufacturing  and  are  made  as  rigid  as  possible  so  as  to 
enable  them  to  do  rapid  work.  All  unnecessary  adjust- 
ments are  dispensed  with  and  the  machine  is  made  with  as 
few  joints  as  possible.  This  class  of  machines  is  intended 
for  grinding  plain  cylindrical  or  slightly  conical  work,  such 
as  spindles,  rolls,  shafts,  etc.  In  all  cases  the  work  runs  on 
dead  centers.  The  universal  grinding  machines  are 
provided  with  more  adjustments,  and  are  adapted  for  grind- 
ing internal  or  external  work  (either  straight  or  tapered), 
cutters,  reamers,  etc. 


CONSTRUCTION  OF  GRINDING  MACHINES. 

84.  Plain  Grinding  Machine.  — Fig.  15  shows  a 
front  and  Fig.  16  a rear  view  of  a plain  grinding  machine, 
made  by  the  Brown  & Sharpe  Manufacturing  Company,  of 
Providence,  Rhode  Island.  The  entire  machine  is  supported 


44 


GRINDING. 


§ 18 

upon  a rigid  base  a.  The  carriage  b can  be  moved  along  the 
base  by  the  hand  wheel  c or  arranged  to  move  back  and 
forth  automatically  by  setting  the  stops  d and  e at  the  de- 
sired places.  The  table  f is  pivoted  upon  the  carriage  b so 
that  it  can  be  brought  parallel  to  the  line  of  travel  or  set  at 
a slight  angle  for  grinding  tapers.  One  end  of  the  carriage  f 
is  graduated  either  in  degrees  or  inches  per  foot,  so  as  to 


assist  in  setting  the  work  to  approximately  the  right  posi- 
tion, the  final  setting  always  being  made  by  trial.  The  head- 
stock  g and  footstock  h are  clamped  to  the  carriage  as  shown. 
The  main  bearing  surface  for  both  headstock  and  footstock 
is  vertical,  as  shown  at  i.  One  object  of  this  is  to  have  the 
main  bearing  for  the  headstock  and  the  footstock  parallel  to 
the  center  line  of  the  work  and  so  arranged  that  differences 
in  the  pressure  used  in  clamping  the  parts,  wear,  etc.  will 


18 


GRINDING. 


45 


have  as  little  influence  on  the  alinement  of  the  work  as  pos- 
sible. Another  object  of  this  design  is  to  so  locate  the  bear- 
ing surfaces  that  they  will  be  protected  from  emery  dust 
and  water  without  the  use  of  guards  that  have  to  be  adjusted 
for  every  change  in  the  length  of  the  work  being  ground. 


Both  centers  are  dead,  that  is,  they  do  not  revolve.  The 
pulley  j is  driven  by  a belt  from  an  overhead  drum  that  is 
driven  by  cone  pulleys,  so  that  the  speed  of  the  work  can  be 
adjusted.  The  dead  centers  are  shown  at  k and  /.  To  assist 
in  supporting  the  work,  fixed  rests  m and  n may  be  used  or 
a follower  rest  may  be  attached  to  the  arm  o.  The  grinding 
wheel  is  carried  upon  the  grinding-wheel  slide  /,  which  is 
well  supported  from  the  floor.  The  grinding-wheel  slide  p 


46 


GRINDING. 


§18 


is  set  on  an  incline  so  that  it  tends  to  slide  away  from 
the  work.  This  removes  all  danger  of  the  wheel  being 


moved  toward  the  work  on  account  of  any  vibration.  The 
emery  wheel  q is  provided  with  a guard  r,  and  provision  is 


Fig.  17. 


GRINDING. 


47 


§18 

made  for  flooding  the  work  with  water  from  the  pipe  s. 
The  water  flows  back  to  the  tanks  /,  from  which  it  is 
pumped  to  the  work  again.  The  emery  wheel  is  driven 
by  belts  from  an  overhead  drum,  and  provision  is  made  for 
varying  the  speed  of  the  wheel  by  a series  of  cone  pulleys. 
The  table  feed  is  driven  by  a belt  on  the  cone  pulley  u . 

The  grinding  wheel  and  grinding-wheel  stand  are  moved 
toward  or  away  from  the  work  by  means  of  the  hand  wheel  v. 
Back  of  the  hand  wheel  v is  arranged  an  automatic  cross- 
feed mechanism  that  will  be  described  later. 

As  previously  stated,  both  the  headstock  and  tailstock 
centers  are  dead.  This  eliminates  errors  in  the  roundness 
of  the  work  due  to  want  of  roundness  in  the  live  spindle,  and 
any  errors  that  might  be  caused  by  the  live  center  running 
out  of  true.  Work  ground  carefully  on  dead  centers  can 
be  reversed  end  for  end  and  will  then  run  so  true  that  even 
a very  sensitive  indicator  will  fail  to  show  any  error.  This 
test  is  so  rigid  that  it  is  very  seldom  that  work  done  be- 
tween centers,  where  one  center  is  a live  one,  will  pass  it 
satisfactorily. 

In  the  machine  described,  the  grinding-wheel  carriage 
stands  still  and  the  work  moves  past  it.  In  the  machines 
manufactured  by  the  Landis  Tool  Company,  of  Waynesboro, 
Pennsylvania,  the  table  carrying  the  work  stands  still  and 
the  grinding-wheel  carriage  moves  along  the  work. 

85.  Universal  Grinding  Machine.  — A universal 
grinding  machine,  as  made  by  the  Brown  & Sharpe  Manu- 
facturing Company,  Providence,  Rhode  Island,  is  shown  in 
Fig.  17.  In  this  particular  design  of  machine,  the  emery 
wheel  a normally  remains  stationary  during  the  grinding  and 
the  work  is  traversed  past  it.  The  guideways  are  formed  on 
top  of  the  base  b , and  serve  to  guide  a long  carriage  c to 
which  the  table  d is  pivoted.  This  table  carries  the  head- 
stock  e and  footstock  which  can  be  clamped'  to  it  in  any 
position  throughout  its  length.  The  emery-wheel  stand  g 
is  mounted  on  a slide  that  normally  is  at  right  angles  to  the 
guideways  on  top  of  the  frame.  This  stand  g can  be  moved 


48 


GRINDING. 


§ 18 

along  its  slide  toward  or  away  from  the  work  by  turning 
the  wheel  n.  The  slide  on  which  the  emery-wheel  stand  is 
mounted  is  pivoted  to  its  base,  to  which  it  can  be  clamped 
at  any  angle  with  the  guideways  that  the  construction  per- 
mits. This  allows  short  conical  work  having  a large  in- 
cluded angle  to  be  ground;  in  that  case  the  table  d carrying 
the  work  will  remain  stationary  while  the  wheel  is  traversed 
past  the  work. 

86.  In  universal  machines  the  headstock  has  a live 
spindle  to  which  a chuck  or  a face  plate. may  be  fitted;  this 
live  spindle  is  driven  by  a belt  from  an  overhead  drum. 
Provision  is  made  for  grinding  on  dead  centers  by  placing 
a loose  pulley  i on  which  a belt  can  be  put,  on  the  end 
of  the  live  spindle,  and  providing  a suitable  arrangement 
for  locking  this  spindle — in  this  case,  a movable  pin  k that 
can  be  inserted  into  a hole  in  the  pulley  /.  The  headstock 
is  placed  on  a base  to  which  it  is  pivoted  in  order  to  allow 
the  axis  of  the  live  spindle  to  be  placed  at  any  angle  with 
the  table  that  the  construction  of  the  machine  permits.  This 
adjustment  permits  conical  work  held  in  the  chuck  or  face 
plate  to  be  ground  without  disturbing  the  setting  of  the 
table  or  of  the  slide  carrying  the  emery-wheel  fixture.  The 
headstock  base,  bottom  of  grinding-wheel  stand,  and  end  of 
the  table  are  all  provided  with  graduations.  These  gradu- 
ations are  used  in  setting  the  different  parts  of  the  machine 
to  approximately  the  desired  angle  for  any  work  in  hand. 

The  carriage  c is  moved  past  the  emery  wheel  by  turning 
the  hand  wheel  m\  it  is  alsp  provided  with  a feed  that  can  be 
automatically  stopped  at  any  point  within  the  range  of 
motion  of  the  carriage. 

87.  The  footstock  of  a grinding  machine  serves  the 
same  purpose  as  the  tailstock  of  a lathe,  but  differs  consid- 
erably from  it  in  it's  general  construction.  The  footstock 
spindle  of  a grinding  machine,  as  a general  rule,  is  provided 
with  some  form  of  a spring  that  operates  it  and  regulates  the 
pressure  with  which  its  center  is  pressed  into  the  center  of 
the  work.  Such  a regulation  of  the  pressure  contributes,  in 


GRINDING. 


49 


§ 18 

a large  measure,  to  the  accuracy  of  the  work,  inasmuch  as 
it  prevents  springing  of  the  work  by  an  excessive  setting  up 
of  the  footstock  center  which  a careless  operator  is  very  apt 
to  do.  This  spring  also  maintains  a constant  pressure  on 
the  center,  even  though  there  may  be  considerable  wear  of 
the  center  hole,  or  the  work  be  lengthened  by  expansion. 

88.  Fig.  18  shows  the  construction  of  the  footstock  of 
the  grinding  machine  made  by  the  Landis  Tool  Company. 
A lever  a is  pivoted  to  the  frame  of  the  footstock;  it  carries 
a pin  b at  one  end  that  is  placed  in  a hole  cut  into  the 
spindle  c.  The  lower  arm  of  this  lever  is  acted  on  by  a 
plunger  d and  a helical  spring  e\  this  spring  tends  to  move 
the  footstock  spindle  forwards.  Obviously,  the  pressure 
with  which  the  footstock  center  presses  against  the  work 
is  that  caused  by  the  tension  of  the  spring  e.  The  tension 


of  this  spring  can  be  regulated  by  means  of  the  adjusting 
screw  f.  For  very  small  work,  even  the  lowest  tension  of 
the  spring  may  cause  enough  pressure  to  bend  the  work,  in 
which  case  the  pressure  may  be  relieved  to  any  desired  ex- 
tent by  screwing  the  nurled  relieving  nut  g against  the  end 
of  the  footstock.  If  this  is  done,  the  operator  must  use 
great  care  not  to  turn  the  relieving  nut  so  much  as  to  loosen 
the  work,  which  can  be  told  by  tightly  grasping  the  work 
and,  while  shaking  it,  observing  if  there  is  any  end  play. 

C.  S . III. —5 


GRINDING. 


51 


§ 18 

Footstocks  are  constructed  in  a number  of  ways  by  the 
different  manufacturers  of  grinding  machines;  it  is  believed 
that  all  of  them,  however,  contain  a provision  of  some  kind 
for  preventing  an  excessive  pressure  on  the  work  in  the 
direction  of  its  axis. 

89-  Overhead  Arrangements.  — Figs.  19  and  20 
show  the  arrangement  of  the  countershafts  for  the  universal 
grinding  machine  illustrated  in  Fig.  17.  Fig.  19  (a)  is  a 
front  view,  Fig.  19  ( b ) a plan  of  the  overhead  arrangements, 


13 

1 

L 

Fig.  20. 


52 


GRINDING. 


§ 18 

and  Fig.  20  an  end  view  of  the  machine.  A tight  and  a 
loose  pulley  a and  a'  are  placed  on  the  countershaft  a" , 
which  is  driven  by  belting  it  to  a line  shaft,  and  which  can 
be  stopped  and  started  by  shifting  the  driving  belt  a'"  by 
means  of  the  shifter  b.  A cone  pulley  c is  keyed  to  the 
countershaft  a"  and  is  belted  to  a cone  pulley  d on  the 
emery-wheel  countershaft  d\  which  carries  the  cylindrical 
pulley  e that  is.  belted  to  and  drives  the  emery-wheel  shaft. 
From  this  arrangement,  it  follows  that  the  emery  wheel  is 
stopped  and  started  by  operating  the  shifter  b.  A cone  pul- 
ley g is  placed  on  the  countershaft  a",  to  which  it  can  be 
attached  by  means  of  a friction  clutch  operated  by  the 
shifter  f.  The  cone  pulley  g is  belted  to  a cone  pulley  h on 
the  headstock  countershaft  h! , which  carries  the  long  cylin- 
drical drum  i that  is  belted  to  the  headstock.  Two  separate 
belts  are  provided  for  driving  the  work,  one  of  which  is  used 
for  grinding  on  dead  centers  and  the  other  for  rotating  the 
headstock  spindle  for  chuck  work  and  face-plate  work.  The 
belt  that  is  not  in  use,  as  the  belt  m in  this  case,  is  removed 
from  the  drum  and  hung  up  where  it  is  out  of  the  way. 
The  different  feeds  are  driven  from  the  headstock  counter- 
shaft h!  by  belting  the  cone  pulley  k to  the  feed  cone  pulley  /. 
By  tracing  out  the  belting,  it  will  be  seen  that  the  work  will 
have  a direction  of  rotation  opposite  to  that  of  the  emery 
wheel.  A rotary  force  pump  is  driven  by  belting  it  to  the 
pulley  n. 

It  is  necessary  in  any  grinding  machine  to  so  arrange  the 
countershafts  that  the  speeds  of  the  emery  wheel  and  of  the 
work  can  be  changed  independently  of  each  other  in  order 
that  the  best  speed  may  be  obtained  for  each.  The  changes 
of  speed  are  usually  obtained  by  placing  the  belts  on  differ- 
ent steps  of  the  cone  pulleys. 

90.  Automatic  Cross-Feed. — The  best  grinding  ma- 
chines are  now  fitted  with  automatic  cross-feeds.  This 
feed  differs  essentially  from  that  of  a lathe,  however, 
in  that  its  purpose  is  not  a constant  movement  of  the 
grinding  wheel  in  a direction  crossing  the  axis  of  the 


§18 


GRINDING. 


53 


work.  Rather,  its  purpose  is  to  automatically  advance 
the  grinding  wheel  a predetermined  distance  toward  the 
axis  of  the  work  as  soon  as  the  wheel  or  the  work  has 
come  to  the  end  of  its  longitudinal  traverse;  the  automatic 
cross-feed  is  intended  to  repeat  this  operation  a prede- 
termined number  of  times  and  then  automatically  stop 
the  advance  of  the  wheel  toward  the  axis  of  the  work.  In 
other  words,  the  automatic  cross-feed  relieves  the  operator 
from  the  necessity  of  feeding  the  grinding  wheel  forwards 
after  each  cut,  and,  furthermore,  when  correctly  set  will 
grind  the  work  to  the  desired  diameter  and  then  automatic- 
ally stop  grinding,  thus  preventing  the  grinding  of  work  too 
small. 


91.  Automatic  cross-feeds  are  constructed  in  various 
ways,  but  the  principle  upon  which  they  work  can  be  illus- 
trated by  a description  of  the  one  illustrated  in  Fig.  21, 
which  shows  the  details  of  the  cross-feed  used  upon  the 
machine  shown  in  Fig.  17.  The  length  of  the  table  stroke 
is  controlled  by  the  stops  i and jf  which  operate  the  lever  g, 
thus  reversing  the  table.  The  cross-feed  is  operated  by  the 
mechanism  attached  to  the  lower  end  of  this  lever  g.  When 
the  hand  wheel  1 1 , a portion  of  which  is  broken  away  in  the 
illustration  to  show  the  details,  is  rotated  in  the  direction  of 
the  arrow,  the  grinding  wheel  is  moved  toward  the  work, 
and  when  rotated  in  the  opposite  direction,  it  is  moved  away 
from  the  work.  The  ratchet  wheel  a is  attached  per- 
manently to  the  hand  wheel  and  contains  a slot  m carrying 
a loose  ring.  To  this  ring  is  attached  a block  /,  the  block 
being  pivoted  to  the  ring  at  n and  being  provided  with  a 
latch  p,  which  is  so  arranged  that  when  it  is  pressed  against 
the  stop  shown  on  its  right,  it  will  move  the  ratchet  one 
tooth.  The  latch  p can  be  disengaged  from  the  ratchet  by 
raising  the  left-hand  end  of  the  block  /,  provision  for  this 
being  made  by  the  slot  which  surrounds  the  screw,  as  shown 
in  the  illustration.  The  block  / carries  a shield  r,  which,  by 
passing  under  the  point  of  the  pawl  b , can  prevent  its 
engaging  the  ratchet  wheel.  The  ratchet  wheel  is  operated 


54 


GRINDING. 


§18 


by  means  of  the  pawl  b , which  is  connected  to  the  lever  c , 
the  latter  being  pivoted  at  d and  being  operated  by  an  in- 
clined block  that  engages  the  lower  end  of  the  lever  g.  The 
amount  that  this  block  engages  the  lever  g is  controlled  by 


the  screw  e and  stop  f.  By  this  means  the  lever  c can  be 
so  adjusted  that  the  pawl  b will  move  the  wheel  through  one 
or  more  teeth  at  each  end  of  the  stroke,  that  is,  whenever 
the  lower  end  of  g is  thrown  across  the  V-shaped  stop 
upon  c. 

92.  Having  described  the  uses  of  the  various  parts,  the 
operation  of  adjusting  the  cross-feed  may  be  described  as 
follows:  The  stroke  of  the  table  k is  adjusted  by  means  of 

the  stops  i and /,  after  which  the  hand  wheel  h is  carefully 
turned  in  the  direction  of  the  arrow  until  the  wheel  nearly 
or  just  touches  the  work.  The  stroke  of  the  table  is  then 
stopped,  and  without  changing  the  hand  wheel  h the  screw  o 


GRINDING. 


55 


§ 18 

is  loosened  and  the  block  / raised  until  the  latch  p is  out  of 
contact  with  the  teeth  of  the  ratchet.  The  block  / is  held 
in  this  position  with  the  right  hand,  while  with  the  left 
hand  the  pawl  b is  swung  into  the  notches  of  the  ratchet, 
after  which  the  block  / is  moved  around  until  the  point  of 
the  throw-out  shield  r is  just  past  the  tooth  occupied  by 
the  pawl  b,  the  pawl  being  lifted  out  of  the  way  to  allow  the 
shield  to  pass.  The  block  l is  then  let  down  so  as  to  bring 
the  latch  p into  contact  with  the  ratchet  once  more,  and  the 
thumbscrew  o tightened.  The  pawl  b is  then  thrown  back 
against  the  shield  r,  which  will  prevent  its  coming  in  contact 
with  the  ratchet.  The  table  stroke  is  next  started,  and  if 
the  pawl  b does  not  engage  the  teeth  of  the  ratchet  when  the 
lever  ^depresses  the  lever  c}  it  may  be  made  do  so  by  press- 
ing one  or  more  times  upon  the  latch  p.  This  is  done  by 
placing  the  thumb  against  the  latch  and  the  forefinger 
against  the  projection  extending  up  from  the  block  /.  The 
pawl  b will  then  turn  the  ratchet  and  hand  wheel,  thus%feed- 
ing  the  emery  wheel  forwards  until  it  cuts  the  work,  the 
pawl  once  more  coming  to  rest  upon  the  shield  r.  Allow 
the  machine  to  run  until  the  cut  is  practically  ended,  stop- 
ping the  table  at  the  footstock  end  of  the  stroke  with  the 
shifter  and  overhead  brake.  Now  measure  the  work,  ascer- 
taining the  quarter-thousandths  to  be  taken  off  to  bring  it 
to  the  correct  size.  Press  the  latch  p once  for  each  quarter- 
thousandth  of  an  inch;  thus,  for  .003  inch,  press  the  latch 
12  times,  start  the  table,  and  the  pawl  will  move  the  ratchet 
until  the  shield  r prevents  the  pawl  b catching  another 
tooth  Allow  the  wheel  to  pass  over  the  work  until  it  shows 
the  same  cut  as  when  the  measurement  was  taken  and  stop 
the  table  at  the  footstock  end,  as  before.  If  a suitable 
wheel  is  used,  the  diameter  will  show  a reduction  of 
.003  inch.  If  the  work  does  not  show  this  reduction,  the 
latch  p is  pressed  once  for  every  quarter-thousandth  further 
reduction  necessary,  and  the  machine  started  up  once  more, 
as  before.  When  the  work  is  the  right  size,  the  pawl  b is 
thrown  out  and,  without  changing  the  position  of  the 
block  /,  the  hand  wheel  h is  turned  in  a direction  opposite  to 


56 


GRINDING. 


§ 18 

that  of  the  arrow  for  about  one  turn.  This  will  remove  the 
emery  wheel  from  the  work.  When  the  next  piece  of  work 
is  in  place  and  the  table  stroke  started,  the  hand  wheel  is 
turned  in  the  direction  of  the  arrow  until  the  emery  wheel 
just  cuts,  then  the  pawl  b is  thrown  into  the  notches  and 
the  machine  allowed  to  continue  its  work  until  the  shield  r 
has  again  stopped  the  feed  by  disengaging  the  pawl  b from 
the  ratchet  wheel.  When  the  emery  wheel  shows  the  same 
cut  that  it  did  when  finishing  the  first  piece,  the  machine  is 
stopped  as  before  and  the  work  measured.  If  the  work  is 
large,  the  latch  p is  pressed  as  many  times  as  the  work  is 
quarter-thousandths  large  and  the  grinding  continued  until 
the  right  dimension  is  obtained.  After  the  wear  of  the 
wheel  has  been  determined,  it  is  possible  to  press  the  latch  p 
the  proper  number  of  times  before  beginning  the  cut  on  each 
new  piece  and  thus  finish  the  piece  to  the  exact  size  at  one 
operation. 

93.  When  setting  the  automatic  cross-feed,  it  must  be 
remembered  that  the  depth  of  each  cut  is  dependent  on  the 
number  of  teeth  the  ratchet  is  moved  at  the  end  of  each 
stroke.  The  number  of  teeth  that  the  ratchet  wheel  is 
moved  at  each  stroke  is  controlled  by  means  of  the  adjust- 
ing screw  which  controls  the  movement  of  the  lever  c and 
the  pawl  b.  The  throw-out  shield  r , by  its  position,  simply 
determines  the  total  depth  of  the  successive  cuts,  that  is, 
the  total  distance  that  the  grinding  wheel  is  moved  toward 
the  work. 

94.  The  diameter  of  the  work  produced  by  the  auto- 
matic cross-feed  should  be  measured  after  the  wheel  has 
stopped  cutting,  or  when  the  amount  of  sparks  given  off 
shows  that  it  is  cutting  at  the  same  rate  that  it  did  when 
the  previous  piece  was  measured.  The  reason  for  this  is 
that  the  grinding  wheel  will  continue  to  reduce  the  diame- 
ter slowly  for  some  time  after  the  feed  has  been  stopped. 

95.  The  cross-slide  on  which  the  wheel  of  a grinding 
machine  is  mounted  must  move  quite  freely  in  order  that 


§18 


GRINDING. 


57 


it  may  be  moved  an  amount  as  small  as  .000125  inch.  In 
order  to  keep  the  wheel  slide  in  good  condition,  it  should  be 
oiled  with  good  oil  each  day  and  moved  throughout  its  entire 
length  during  the  operation,  so  as  to  insure  thorough  lubri- 
cation. If  the  wheel  slide  is  allowed  to  remain  stationary 
for  some  time  without  lubrication,  it  may  be  necessary  to 
clean  the  parts  before  they  will  work  freely  again,  though 
usually  the  working  of  a good  quality  of  oil  through  the  oil 
holes  and  the  moving  of  the  parts  throughout  their  entire 
travel  several  times  will  put  the  working  parts  in  good 
condition. 

96.  The  automatic  cross-feed  is  a valuable  addition  to 
the  grinding  machine,  on  account  of  the  fact  that  -it  not 
only  enables  the  operator  to  attend  to  other  details  while 
the  piece  is  grinding,  thus  saving  much  time,  but  by  uniform 
movement  it  maintains  the  proper  condition  of  the  emery 
wheel  and  increases  its  sizing  power.  This  latter  feature  is 
one  that  has  received  very  little  attention  in  the  past,  but  is 
of  great  importance  if  it  is  desired  to  finish  duplicate  pieces. 


GRINDING. 

(PART  2.) 


GRINDING  SOLIDS  OF  REVOLUTION. 


ADVANTAGES  OF  GRINDING. 

1.  When  grinding  machines  were  first  designed,  they 
were  used  almost  entirely  for  hardened  work,  the  prevailing 
idea  being  that  grinding  was  a refined  perfecting  process 
suitable  only  for  the  finishing  of  hardened  work  that  re- 
quired a great  degree  of  accuracy.  This  idea  still  prevails 
in  many  quarters,  but  it  is  incorrect,  since  experience  has 
shown  that  whenever  a suitable  grinding  machine  is  intelli- 
gently used  the  accuracy  that  may  be  attained  when  soft 
work  is  finished  by  grinding  is  accompanied  by  a reduction 
in  the  cost  of  the  work  over  that  which  has  been  accom- 
plished by  other  processes.  Thus,  many  kinds  of  cylin- 
drical work,  such  as  shafts,  spindles,  studs,  arbors,  etc.  that 
are  made  of  soft  steel  may  be  turned  to  nearly  the  finished 
size,  and  then  by  careful  filing,  followed  by  an  intelligent 
application  of  emery  cloth,  brought  to  the  correct  size.  By 
using  a grinding  machine,  however,  most  of  the  cost  of  the 
files  and  emery  cloth  is  eliminated  from  the  charges  against 
the  work;  furthermore,  the  quantity  of  metal  left  for  finish- 
ing can  be  removed  much  faster  by  grinding  than  by  filing 
or  turning  in  the  lathe,  at  least  on  work  that  is  within  the 
capacity  of  the  grinding  machine. 

§ 19 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


GRINDING. 


§19 


2.  It  has  been  shown  in  actual  practice  that  a grinding 
machine  fitted  with  a 12-inch  grinding  wheel,  which  is  a 
common  size,  will  reduce  a cylindrical  piece  of  steel  from 
.005  inch  to  .012  inch  in  diameter  in  less  time  than  would 
be  consumed  in  reducing  the  diameter  an  equal  amount 
in  a lathe.  With  especially  heavy  and  powerful  grinding 
machines,  a greater  amount  than  that  named  above  can  be 
removed. 

3.  While  the  grinding  machine  may  in  the  future  be 
developed  sufficiently  to  adapt  it  for  roughing  out  work,  it 
is  not  developed  enough  for  that  at  present,  and  the  work 
must  come  to  the  grinding  machine  roughed  out  to  within 
.005  inch  to  y1^  inch  of  the  finished  size  in  order  that  the 
machine  may  not  work  at  a serious  disadvantage.  When 
the  amount  of  metal  to  be  removed  is  within  the  limits 
stated,  grinding  is  not  only  an  economical,  but  is  also  a very 
desirable,  finishing  process  on  account  of  the  great  accuracy 
attainable. 

4.  An  emery  wheel  having  a diameter  of  18  inches  and 
a face  | inch  wide,  when  running  at  its  ordinary  speed,  pre- 
sents approximately  2,500,000  cutting  points  to  the  work 
in  1 minute,  and  a wheel  of  the  same  diameter,  but  having 
a face  1^-  inches  wide,  presents  about  5,000,000  cutting 
points  to  the  work  in  the  same  period  of  time.  Each  of 
these  cutting  points  removes  a very  small  amount  of  metal; 
but  when  the  aggregate  amount  is  considered  it  is  compar- 
atively large.  Furthermore,  in  modern  grinding  machines 
the  cutting  points  pass  over  from  1 to  4 square  feet  of  sur- 
face per  minute.  The  statements  just  made  will  serve  to 
explain  why,  within  reasonable  limits,  the  grinding  machine 
can  remove  metal  faster  than  the  lathe,  with  its  single 
cutting  point. 

5.  The  purposes  and  advantages  of  machine  grinding- 
may  be  briefly  summed  up  as  follows:  In  the  first  place,  it 
is  economical  to  finish  work  to  size  by  grinding;  in  the 
second  place,  the  accuracy  attainable  is  very  great.  The 
first  advantage  named  is,  today,  the  most  important  one, 


GRINDING. 


3 


§ 19 


and  fits  the  grinding  machine  for  manufacturing  purposes 
on  work  within  its  range  and  capacity;  accuracy  is  given 
the  second  place,  because  the  accuracy  readily  attainable 
by  grinding  is  far  beyond  that  which  is  necessary  on  most 
duplicate  work. 


SELECTION  AND  USE  OF  GRINDING  WHEEL. 


SELECTION  OF  WHEEL. 

6.  Grade. — In  order  that  the  grinding  wheel  used  in 
machine  grinding  may  cut  freely,  that  is,  with  little  or  no 
pressure,  it  is  desirable  that  the  wheel  be  “self-sharpening.” 
A self -sharpening  grinding  zvheel  is  one  in  which  the  dulled 
particles  of  the  abrasive  material  break  away  readily  during 
the  grinding  operation,  and  the  ease  with  which  these  par- 
ticles become  detached,  or  the  resistance  that  they  offer  to 
breaking  out,  determines  the  grade  of  the  wheel.  Thus,  if 
the  particles  break  away  readily,  the  wheel  is  said  to  be 
soft,  while  one  that  offers  considerable  resistance  to  the 
detaching  of  the  dulled  particles  is  called  hard.  From 
this  explanation  it  should  be  plain  that  the  terms  “soft” 
and  “hard,”  when  applied  to  a grinding  wheel,  do  not  refer 
to  the  relative  hardness  of  the  abrasive  material,  but  merely 
to  the  facility  with  which  the  dulled  particles  become 
detached. 

7 . Causes  of  Glazing. — It  is  evident  that  the  longer 
the  dulled  particles  are  retained,  the  duller  will  they  become, 
and  that,  consequently,  more  pressure  will  be  required  to 
make  them  cut.  Undue  dulling  of  the  particles  is  also 
caused  by  an  excessive  speed.  The  dulling  of  the  particles 
manifests  itself  by  the  glazed  appearance  of  the  cutting  sur- 
face of  the  grinding  wheel,  and  by  considering  the  causes 
of  this  glazing  we  would  be  justified  in  drawing  the  conclu- 
sion that  a wheel  that  glazes  rapidly  is  either  too  hard  for 
the  work  it  is  performing  or  is  run  too  fast.  A wheel  that 


4 


GRINDING. 


§ 19 

requires  much  pressure  to  make  it  cut  will  not  produce  the 
best  results,  no  matter  how  rigid  the  machine  in  which  it  is 
used  may  be,  for  the  reason  that  the  pressure  of  the  grind- 
ing will  disturb  both  the  axis  of  the  wheel  and  the  axis  of 
the  work. 

8.  Influence  of  Hardness  of  Material. — Since  dif- 
ferent materials  vary  in  their  hardness,  the  rate  at  which 
they  will  dull  the  grinding  wheel  also  varies.  Naturally, 
the  harder  material  will,  dull  the  abrasive  substance  incorpo- 
rated in  the  wheel  more  rapidly  than  will  the  softer  material ; 
from  this  we  may  draw  the  conclusion  that  the  harder 
the  material  is,  the  softer  should  be  the  grade  of  the  grinding 
wheel . Because  of  this  fact,  it  should  be  remembered,  when 
considering  the  working  of  different  grades  of  steel,  that 
since  high-carbon  steels  are  harder  than  steels  containing 
only  a low  percentage  of  carbon,  they  require  a softer  grind- 
ing wheel,  while  low-carbon  steels  can  be  advantageously 
ground  with  a wheel  that  is  harder  and  denser. 

9.  The  different  high-carbon  steels  of  the  variety  known 
among  shopmen  as  “tool  steel”  vary  but  little  in  their 
relative  hardness,  and,  consequently,  a wheel  suitable  for 
one  kind  of  such  high-carbon  steel  will  work  satisfactorily 
on  most  other  grades  of  such  steel.  Steel  that  is  low  in 
carbon,  commonly  called  “machinery  steel”  by  shopmen,  is 
quite  soft,  and  experience  has  shown  that  it  can  probably 
be  ground  best  by  using  a combination  wheel,  which  is 
a wheel  in  which  several  sizes  of  grains  are  incorporated. 
Thus,  a wheel  in  which  No.  36,  46,  60,  80,  and  100  emery 
is  incorporated  is  a combination  wheel  that  is  suitable  for 
some  kinds  of  work. 

10.  Influence  of  Vibration  of  Work. — The  steadi- 
ness of  the  revolving  work  while  it  is  being  ground  must  be 
considered  in  deciding  on  the  grade  of  the  wheel  that  is  to  be 
used.  If  the  work  vibrates  somewhat,  the  wheel  should  be 
harder  than  if  the  same  work  was  perfectly  free  from  vi- 
bration. The  reason  for  using  a harder  wheel  is  that  the 
vibration  of  the  work  has  the  same  effect  on  the  cutting 


GRINDING. 


5 


§ 

surface  of  the  wheel  as  a succession  of  hammer-blows,  which 
would  break  the  particles  of  the  abrasive  material  away  too 
rapidly  if  a soft  wheel  were  used. 


DIRECTIONS  FOR  SELECTING  WHEELS. 

11.  In  order  to  aid  the  grinding-machine  operator  in 
selecting  a suitable  wheel,  the  Landis  Tool  Company  publish 
the  directions  given  below,  where  the  grade  of  the  wheel  is 
given  in  accordance  with  the  standard  of  the  Norton  Emery 
Wheel  Company. 

12.  Wheels  for  External  Grinding. — For  grinding 
hardened  steel,  in  roughing  it  down  to  nearly  the  desired 
size,  use  a No.  GO  emery  wheel,  grades  K to  M ; for  finish- 
ing hardened  steel,  according  to  the  degree  of  finish  desired, 
use  a No.  60,  80,  100,  120,  or  150  emery  wheel  of  the  grades 
I to  M.  For  roughing  soft  steel  down  to  nearly  the  finished 
size,  use  wheels  from  No.  46  to  No.  60  of  the  grades  M,  N,or  O ; 
and  for  finishing  soft  steel,  use,  according  to  the  degree  of 
finish  desired,  wheels  from  No.  60  to  No.  180  of  the  grades  L 
or  M.  For  roughing  cast  iron  down  to  nearly  the  finished 
size,  use  wheels  from  No.  46  to  No.  60,  and  of  the  grades  G 
to  K;  for  finishing  cast  iron,  use  wheels  from  No.  60  to 
No.  80  of  the  grades  K to  M.  To  finish  brass  or  bronze, 
use  a wheel  from  No.  60  to  No.  120,  according  to  the  degree 
of  finish  desired,  and  of  the  grades  F to  K. 

13.  Wheels  for  Internal  Grinding. — -For  roughing 
out  soft  or  hardened  steel,  use  a wheel  from  No.  46  to  No.  60 
of  the  grades  G to  K,  and  for  finishing  soft  or  hardened 
steel,  use  a wheel  from  No.  60  to  No.  100  of  the  grades  E 
to  F.  For  roughing  out  brass  or  bronze,  use  the  same 
wheels  as  for  roughing  out  steel;  for  finishing  brass  or 
bronze,  use,  according  to  the  degree  of  finish  desired,  a 
wheel  from  No.  80  to  flour  emery  of  the  grades  E to  F. 

14.  The  directions  here  given  should  be  considered 
merely  as  an  aid  in  selecting  a wheel.  The  results  must  be 


6 


GRINDING. 


§ 19 


observed  and  the  wheel  then  changed  to  suit,  if  found  un- 
satisfactory. The  Brown  & Sharpe  Manufacturing  Com- 
pany recommend  that  for  internal  grinding  only  corundum 
wheels  be  used. 

1 5.  Shapes  of  Wheels. — Emery  wheels  and  similar 
grinding  wheels  are  made  in  various  shapes  by  the  different 
manufacturers;  some  of  the  shapes  most  commonly  used  in 


(b) 


(g)  (h) 


Fig.  1. 

machine  grinding  are  given  in  Fig.  1.  Wheels  having  the 
shape  of  a flat  circular  disk  with  a small  central  hole,  as 
the  one  shown  in  Fig.  1 (a),  are  used  for  external  grinding, 
the  cutting  being  done  by  the  periphery.  The  wheels  most 
commonly  used  on  universal  grinding  machines  have  large 


19 


GRINDING. 


7 


central  holes,  as  shown  in  Fig.  1 ( b ).  Such  wheels  are 

mounted  on  special  arbors  or  upon  bushings  on  an  ordinary 
arbor.  Cupped  wheels  like  the  one  shown  in  Fig.  1 (c)  are 
usually  mounted  directly  upon  the  spindle  and  are  used  for 
surface  grinding,  the  face  a being  used  for  this  purpose. 
Sometimes  these  wheels  are  made  without  the  shoulder  for 
attaching  them  to  a spindle,  in  which  case  they  are  simply 
plain  cylinders.  Such  wheels  are  mounted  in  a chuck  and 
used  for  surface  grinding.  If  the  wheel  shown  in  Fig.  1 ( b ) 
had  a face  several  inches  wide,  it  could  be  used  for  surface 
grinding  by  mounting  it  in  a chuck,  the  work  being  done 
upon  the  face  a.  A wheel  that  has  the  shape  shown  in 
Fig.  1 ( d ) is  used  for  grinding  close  to  the  shoulder  of  work 
that  has  a very  large  flat  shoulder;  the  shape  of  the  wheel 
permits  this  to  be  done  since  it  allows  the  face  of  the  nut 
that  fastens  the  wheel  to  the  spindle  to  come  below  the 
face  a of  the  wheel.  The  grinding  is  done  by  the  periphery 
of  the  wheel. 

16.  A narrow  conical  wheel,  like  the  one  shown  in 
Fig.  1 (<?),  is  much  used  for  grinding  the  clearance  of  ream- 
ers, milling  cutters,  and  similar  cutting  tools  in  cutter-grind- 
ing machines,  in  which  case  the  wheel  is  used  dry.  The 
narrow  face  of  this  wheel  will  not  grind  as  fast  as  a 
wide-faced  wheel,  neither  will  it  generate  as  much  heat, 
which  fact  makes  the  narrow-faced  wheel  more  suitable  for 
dry  cutter  grinding  than  the  wide-faced  wheel.  A beveled 
wheel  of  the  shape  shown  in  Fig.  1 (f)  is  much  used  for 
sharpening  the  teeth  of  narrow  formed  cutters,  as,  for  in- 
stance, gear-cutters;  the  grinding  is  usually  done  by  the 
inside  face,  the  conical  surface  a just  clearing  the  back  of 
the  next  tooth  of  the  cutter.  A recessed  wheel  of  the  form 
shown  in  Fig.  1 (g)  is  used  for  grinding  a square  shoulder 
on  cylindrical  work,  and  like  the  cupped  wheel  illustrated  in 
Fig.  1 (c),  it  can  be  used  for  surface  grinding  on  light  work, 
such  as  the  measuring  surfaces  of  caliper  gauges.  For  in- 
ternal grinding  of  small  holes,  the  wheel  may  assume  the 
shape  shown  in  Fig.  1 (/i). 

C.  S.  III.— 6 


8 


GRINDING. 


§ 19 

1 7.  As  far  as  the  shape  of  the  face  of  the  wheel  is  con- 
cerned, the  wheel  may  be  turned  with  a diamond  tool  to 
almost  any  form  desired.  For  regular  work  in  automatic 
grinding  machines,  the  cutting  face  of  the  wheel  is  usually 
either  a flat  surface,  as  the  side  of  a wheel,  or  the  surface 
of  a cylinder.  These  two  elementary  forms  are  modified  to 
suit  special  conditions. 


SPEEDS  AND  FEEDS. 

1 8.  Surface  Speed  of  Grinding  Wheel  and  Work. 

The  relation  between  the  surface  speeds  of  the  grinding 
wheel  and  the  work  will  become  clear  when  we  consider  as  a 
parallel  case  the  relation  between  the  cutting  speed  of  a 
milling  cutter  and  the  feed  of  the  work  in  a milling  machine; 
since  the  act  of  revolving  a piece  of  work  in  the  grinding 
machine  may  be  likened  to  the  feed  of  the  work  in  a milling 
machine,  while  the  cutting  points  of  a grinding  wheel  may 
be  likened  to  the  cutting  edges  of  a milling  cutter. 

19.  Suppose  that  a milling  cutter  is  cutting  steel,  run- 
ning at  a surface  speed  suitable  for  a proper  maintenance  of 
the  cutting  edges;  there  is  then  one  particular  feed  of  the 
work  at  which  the  cutter  will  work  at  its  best,  and  if  this 
rate  of  feed  is  increased  too  much,  the  teeth  of  the  cutter 
will  be  broken  off.  If  the  milling  cutter  is  speeded  too 
high,  the  heat  generated  by  the  cutting  operation  will  be 
sufficient  to  draw  the  temper  in  the  cutting  edges,  which 
are  rapidly  dulled  in  consequence  of  the  excessive  speed. 
Also,  if  the  milling  cutter  is  speeded  to  the  proper  cutting 
speed  while  the  work  is  fed  so  slowly  that  the  cutter  may  be 
said  only  to  rub  the  work  instead  of  taking  a distinct  chip, 
its  cutting  edges  will  be  rapidly  dulled. 

20.  Considering  now  a grinding  wheel,  if  we  revolve  it 
at  the  proper  speed  but  revolve  the  work  too  fast,  there  will 
be  too  much  stress  upon  the  cutting  points  (the  particles  of 
the  abrasive  material),  which,  consequently,  will  break 
away,  thereby  rapidly  changing  the  diameter  of  the  wheel. 
This  change  in  diameter  will  produce  a corresponding  change 


GRINDING. 


9 


in  the  diameter  of  the  work.  In  other  words,  too  great  a sur- 
face speed  of  the  work  reduces  the  diameter  of  the  wheel 
too  rapidly  and  thus  destroys  its  sizing  power. 

21.  When  the  grinding  wheel  is  run  at  too  high  a speed 
while  the  work  is  revolving  at  a proper  speed,  the  wheel  will 
rapidly  dull  and  become  glazed  on  account  of  the  heat  gen- 
erated. In  the  case  of  a grinding  wheel  running  at  the 
proper  surface  speed,  but  on  work  that  is  revolving  too 
slowly,  the  wheel  will  dull  rapidly  because  there  is  not 
enough  stress  on  the  cutting  points  to  break  them,  and  this 
dulling  will  be  intensified  by  the  heat  that  is  generated. 
When  the  wheel  is  run  at  too  low  a speed,  the  speed  of 
grinding  is  proportionately  reduced. 

. 22.  Practice  has  shown  that  for  the  grinding  wheel 
a surface  speed  of  6,000  feet  per  minute  is  suitable  for 
hardened  steel,  cast  iron,  and  chilled  iron.  For  grinding 
soft  steel  and  other  metals  except  those  named,  the  grinding 
wheel  may  be  given  a surface  speed  of  7,000  feet  per  minute. 
The  average  surface  speed  of  the  work  is  100  feet  per 
minute,  but  it  may  be  considerably  higher  under  certain 
conditions.  For  instance,  suppose  the  operator  to  have  a 
wheel  in  his  machine  that  was  suitable  for  a job  just  fin- 
ished, but  which  is  a little  too  hard  for  the  new  work.  In 
such  a case,  provided  of  course  that  the  difference  in  the 
grade  of  the  required  wheel  and  the  available  wheel  is  not 
too  great,  the  operator  may,  by  slowing  down  the  speed  of 
the  wheel  and  increasing  the  speed  of  the  work,  get  satisfac- 
tory results. 

23.  Chatter  Marks.  — It  often  occurs  in  machine 
grinding  that  the  ground  surface  has  a peculiar  wavy 
appearance  to  which  operators  have  given  the  name  of 
chatter  marks.  These  marks  may  be  due  to  a number  of 
different  causes,  each  one  of  which  may  act  by  itself  or  in 
conjunction  with  the  others.  The  most  common  causes  are 
improperly  supported  work,  looseness  of  the  grinding-wheel 
spindle  in  its  bearings,  and  too  hard  a wheel.  Work  lacking 
inherent  stiffness  should  be  supported  by  proper  steady 


10 


GRINDING. 


19 


rests;  a loose  grinding-wheel  spindle  can  be  cured  by 
tightening  the  bearings;  but  a wheel  that  is  too  hard  is  best 
replaced  by  a softer  one.  Asa  makeshift  it  is  often  possible 
to  make  a hard  wheel  cut  without  chattering  by  turning 
down  the  wheel  with  a diamond,  and  so  narrowing  its  cut- 
ting surface.  If  this  is  done,  it  must  be  remembered  that 
the  amount  of  work  that  can  be  done  per  minute  is  lessened, 
since  the  amount  of  material  removed  by  a grinding  wheel 
depends  directly  on  the  width  of  the  cutting  surface  in  con- 
tact with  the  work.  From  this  it  follows  that  a reduction 
in  the  width  of  the  wheel  calls  for  a finer  feed. 

24.  I n some  cases,  the  ground  surface  may  have  a 
mottled  appearance,  or  it  may  be  full  of  ridges  that  are 
either  parallel  to  the  axis  of  the  work  or  wind  around  it 
like  a thread.  This  appearance  of  the  work  is  due  to  any 
one  of  a number  of  causes,  among  which  may  be  mentioned 
vibration  of  the  piece,  too  slow  or  too  fast  speeds  for  the 
wheel  or  work,  centers  not  in  good  contact,  inequalities  in 
the  stock,  work  not  suitably  supported,  or  a glazed  wheel. 
When  a wheel  is  glazed,  it  is  probable  that  there  are  one 
or  more  spots  on  the  circumference  of  the  wheel  that  are 
sharper  than  the  remainder;  these  sharp  spots  may  be 
likened  to  the  cutting  edges  of  a milling  cutter  that  has  but 
few  teeth.  In  consequence,  the  cutting  is  intermittent, 
and  the  ridges,  which  may  be  likened  to  the  revolution 
marks  of  a milling  cutter,  appear.  The  best  remedy  is  to 
select  a softer  wheel. 

25.  Truing  the  Wheel. — It  is  essential  to  good  grind- 
ing that  the  grinding  wheel  should  fun  very  true  and  bear 


Fig.  2. 


evenly  against  the  work  over  its  entire  cutting  surface.  A 
diamond  tool  is  absolutely  necessary  for  truing  the  wheel, 


19 


GRINDING. 


11 


a good  form  of  which  tool  is  shown  in  Fig.  2.  A small 
diamond  a is  set  centrally  into  the  end  of  a cylindrical  rod 
or  shank  b,  to  the  other  end  of  which  is  fitted  a suitable 
wooden  handle.  Sometimes  the  diamond  is  set  into  a rect- 
angular shank,  but  if  this  is  done,  the  diamond  can  be  used 
in  only  two  or  four  different  positions,  and  hence  the  round 
shank  is  better  for  general  work. 

26.  There  are  various  ways  of  applying  the  diamond- 
pointed  tool  to  the  wheel.  Some  machines  have  devices  for 
holding  it,  but  in  practice  a grinding-machine  operator  will 
usually  find  it  more  convenient  to  do  the  truing  by  hand, 
resting  the  tool  on  the  footstock  center  and  steadying  it  by 
bearing  against  the  end  of  the  work,  the  latter  being  sta- 
tionary. While  holding  the  diamond  tool  steadily  in  place, 
the  revolving  wheel  is  moved  back  and  forth  past  the  tool, 
or  vice  versa;  with  a little  care,  it  is  quite  easy  thus  to  pro- 
duce a true  running  wheel  that  has  a cutting  surface  parallel 
to  the  line  of  motion. 

27.  Beginners  are  very  likely  to  overlook  the  necessity 
of  having  a wheel  run  exactly  true  and  having  it  cut  evenly 
throughout  its  width;  if  this  is  not  the  case,  the  wheel  is 
very  liable  to  make  a cut  so  rough  that  a beginner  will 
misjudge  the  wheel  and  pronounce  it  too  coarse  and  un- 
suitable for  the  work,  while  in  reality  the  same  wheel  if 
properly  trued  would  produce  an  even  and  smooth  surface. 
If  the  wheel  does  not  cut  over  its  entire  surface,  i.  e. , if  the 
cutting  surface  is  not  parallel  to  the  line  of  motion,  it  is 
not  possible  to  feed  at  the  proper  rate  without  showing  dis- 
tinct feed-marks  in  the  form  of  spiral  lines  running  around 
the  work.  The  beginner  is  likely  to  attribute  these  feed- 
marks  to  too  rapid  a feed,  when  in  reality  they  are  due  to  an 
improperly  trued  wheel. 


INFLUENCE  OF  TEMPERATURE. 

28.  Local  Heating  and  Its  Prevention.  — When 
grinding  solids  of  revolution  in  a grinding  machine,  the 
work  and  the  wheel  are  often  flooded  with  water  for  the 


12 


GRINDING. 


§ 19 

purpose  of  carrying  away  the  heat  generated  by  the  grind- 
ing operation.  The  work  is  thus  kept  at  a temperature  that 
is  uniform  enough  to  prevent  a sensible  change  in  the  out- 
line of  the  work. 

29.  Any  one  who  has  done  lathe  work  knows  how  hot 
the  work  becomes  under  the  influence  of  the  cutting  opera- 
tion; and  as  in  grinding,  the  cutting  is  done  much  more 
rapidly,  and,  besides,  by  a great  number  of  cutting  points, 
the  local  heating  of  the  work  at  the  place  where  the  grind- 
ing is  being  done  is  more  pronounced.  Now,  even  if  the 
rise  in  temperature  is-  so  slight  that  the  bare  hand  cannot 
detect  it,  a local  heating  of  any  piece  of  work  will  cause 
a change  in  the  outline  of  the  piece  that  is  greater  than 
is  ordinarily  supposed.  This  change  in  outline  becomes 
very  apparent  in  a grinding  machine,  in  which  under  proper 
conditions  a grinding  wheel  is  capable  of  showing  an  error 
as  small  as  .000005  inch,  the  error  becoming  apparent  by  the 
increase  or  diminution  of  the  sparks  coming  from  the  wheel 
when  cutting. 

30.  The  influence  of  local  heating  on  the  quality  of  the 
work  is  well  shown  when  an  attempt  is  made  to  grind  dry  a 
slender  cylindrical  piece  of  steel  between  centers.  As  the 
grinding  passes  back  and  forth  over  the  work,  the  operator 
will  notice  that  sometimes  the  wheel  is  grinding  more  on 
one  side  of  the  work  than  on  the  other,  and  at  other  times, 
it  will  grind  on  one  side  only.  Passing  over  the  work 
again,  the  wheel  may  cut  on  the  opposite  side,  then  it  may 
cut  at  right  angles  to  where  it  last  cut,  and  so  on.  No 
matter  how  long  the  grinding  continues,  the  cylinder  will 
not  become  round. 

31.  The  following  considerations  explain  why  the  work 
does  not  become  round.  Suppose  we  hold  a round  bar  or 
piece  of  steel  in  our  hands  and  press  a point  about  midway 
between  its  ends  against  an  emery  wheel.  Then,  the  grind- 
ing will  cause  a local  heating  at  the  point  in  contact  with 
the  wheel,  and,  consequently,  the  side  of  the  bar  that  is 
toward  the  wheel  will  elongate,  thus  causing  the  ends  of  the 


19 


GRINDING. 


13 


bar  to  curve  away  from  the  wheel.  Now  assume  that  the 
bar  of  steel  is  placed  between  centers  in  a grinding  machine, 
and  that  the  wheel  is  again  cutting  midway  between  the 
ends.  Then,  as  in  the  previous  case,  the  side  of  the  bar  in 
contact  with  the  grinding  wheel  will  elongate,  but  as  the 
ends  cannot  curve  away  from  the  wheel,  since  they  are 
held  by  the  centers,  the  middle  of  the  bar  will  curve  toward 
the  wheel.  The  fact  that  the  bar  may  be  revolving  does 
not  alter  the  case,  since  the  point  where  the  grinding  is 
taking  place  is  always  hotter  than  the  opposite  side  of  the 
bar.  If  the  wheel  is  passed  back  and  forth  over  the  bar,  it 
is  easily  seen  that  the  side  of  the  bar  where  the  sparks  show 
will  be  constantly  elongated,  and  if  the  piece  being  ground 
is  entirely  free  from  internal  stresses  and  of  absolutely  uni- 
form density,  it  will  be  ground  round,  but  smallest  at  the 
middle.  Unfortunately  the  ideal  condition  of  a piece  of 
work  free  from  internal  stresses  and  of  uniform  density  does 
not  occur  in  practice;  and,  in  consequence,  the  elongation 
of  the  bar  will  not  be  uniform  throughout  each  revolution. 
Hence  the  bar  will  bend  a varying  amount  toward  the  wheel, 
and  as  this  is  still  further  varied  by  the  additional  heat  due 
to  the  increased  depth  of  cut,  owing  to  greater  elongation  at 
certain  points,  the  result  is  a bar  that  is  neither  round  nor 
straight. 

32.  The  remedy  for  the  troubles  due  to  change  of  tem- 
perature is  simple:  flood  the  work  with  sufficient  water  to 
maintain  a uniform  temperature  and  use  a suitable  wheel. 

33.  Noting  the  Sparks.  — In  regard  to  the  sparks 
being  an  indication  of  the  grinding,  it  may  be  interesting 
to  know  that  the  amount  of  metal  that  is  removed  when 
sparks  are  just  visible  has  been  ascertained  by  experiment. 
A hardeped-steel  plug  gauge  about  1 inch  in  diameter  was 
placed  between  the  centers  of  a grinding  machine  and  was 
carefully  ground  to  run  true,  allowing  it  to  pass  back  and 
forth  past  the  wheel  until  all  sparks  ceased.  Its  size  was 
then  noted  by  careful  measurement  in  a standard  measur- 
ing machine  and  it  was  again  placed  in  the  machine.  The 


14 


GRINDING. 


§19 


grinding  wheel  was  now  very  carefully  moved  toward  the 
work  until  sparks  just  became  visible  and  was  then  passed 
back  and  forth  past  the  wheel  until  all  sparks  ceased.  By 
carefully  measuring  the  work  again,  it  was  found  that  the 
piece  had  been  reduced  .00001  inch  in  diameter,  which 
showed  that  the  depth  of  the  cut  was  only  .000005  inch. 
This  experiment  showed  that  the  grinding  wheel  when 
used  in  a good  machine  is  one  of  the  most  sensitive  indica- 
tors of  error. 

34.  When  grinding  work,  the  operator  can  judge  the 
accuracy  with  which  it  is  being  ground  by  noting  the  in- 
crease or  decrease  in  the  volume  of  the  sparks  during  the 
revolution  of  the  work,  and  an  experienced  operator  can 
closely  tell  the  amount  of  error  from  the  relation  between 
the  depth  of  cut  and  the  volume  of  sparks.  This  relation 
can  only  be  studied  in  actual  grinding  by  noting  the  volume 
of  sparks  emanating  from  a grinding  wheel  fora  given  move- 
ment of  the  wheel  slide,  as  indicated  by  the  dial  of  the  ad- 
justing screw.  Since  the  increase  or  decrease  in  the  volume 
of  the  sparks  is  an  indication  of  error,  it  follows  that  an 
operator  having  a knowledge  of  the  amount  of  error  thus 
indicated  may  eliminate  or  reduce  many  errors  by  making 
proper  adjustments. 


GRADUATIONS. 

35.  Purpose  of  Graduations. — The  success  of  the 
grinding  machine  in  grinding  solids  of  revolution  accurately 
to  a predetermined  shape,  as,  for  instance,  true  cylinders 
or  frustums  of  cones,  depends  largely  on  the  provision  of 
suitable  means  for  adjusting  the  line  of  motion  of  the  grind- 
ing wheel  or  the  table  in  relation  to  the  axis  of  rotation  of 
the  work.  These  provisions  are  amply  made  in  the  better 
class  of  grinding  machines  that  are  built  today. 

36.  In  order  to  aid  the  operator  in  setting  the  machine 
to  grind  cylindrical  or  tapering  work,  all  modern  grinding 
machines  have  one  end  of  the  table,  which,  as  previously 
explained,  can  be  swung  around  in  a horizontal  plane, 


GRINDING. 


15 


§19 

graduated  either  to  degrees  or  to  read  to  tapers  in  inches  per 
foot.  These  graduations  are  intended  to  assist  the  operator 
insetting  the  table  approximately  to  the  correct  position; 
it  is  to  be  distinctly  understood  that  for  exact  grinding,  the 
means  of  sensitive  adjustment  with  which  the  table  is  pro- 
vided are  to  be  used  after  it  has  been  determined  by  trial 
where  the  ground  work  differs  from  the  desired  shape. 

37.  Final  Adjustment. — When  setting  the  machine, 
the  operator  should  set  the  table  by  the  graduations  as  nearly 
as  can  be  judged  by  eye.  It  is  entirely  unnecessary  to  use 
a magnifying  glass  for  this  purpose.  The  rough  work  is 
now  placed  in  the  machine 'and,  by  measurement,  it  is  de- 
termined which  end,  if  either,  is  the  larger.  A very  light 
cut  is  now  taken,  observing  if  the  cut  is  heavier  at  the  larger 
end,  which  obviously  should  be  the  case.  If  this  is  not 
the  case,  the  table  is  carefully  adjusted  until  the  cut  shows 
heavier  at  the  larger  end,  which  is  indicated  by  the  sparks. 
The  work  is  now  ground  evenly  and  is  then  measured,  but 
if  one  end  is  too  large,  the  table  is  adjusted  once  more;  this 
cycle  of  operations  is  repeated  until  the  table  is  correctly  set. 

38.  The  main  reason  why  the  graduations  cannot  and 
should  not  be'relied  on  when  accurate  work  is  desired  is  not 
that  the  graduations  are  incorrect,  but  that  any  changes  of 
temperature  of  the  machine  will  affect  the  relative  position 
of  the  various  parts;  any  error  due  to  this  cause  will  be 
doubled  in  the  work.  Another  reason  is  the  unequal  wear 
of  the  centers  that  is  liable  to  occur  with  constant  use,  the 
centers  wearing  out  of  line;  any  error  in  alinement  due 
to  this  cause  will  also  be  doubled.  Thus,  if  one  center  is 
.00025  inch  out  of  line  in  one  direction  and  the  other  center 
is  the  same  amount  out  of  line  in  an  opposite  direction,  the 
total  error  in  alinement  is  .0005  inch,  and  the  error  of  the 
work  will  be  .001  inch.  A slight  amount  of  dirt  or  oil  in 
the  holes  in  which  the  centers  are  placed  will  cause  a corre- 
sponding error  in  alinement. 

39.  Adjustment  of  Headstock. — The  headstock  of 
a universal  grinding  machine  is  generally  arranged  so  that 


1G 


GRINDING. 


§ 19 


it  can  be  swiveled;  graduations  on  its  base  indicate  ap- 
proximately the  angle  at  which  the  spindle  is  set  to  the  line 
of  motion;  provided,  however,  that  the  table  itself  is  set  at 
zero.  When  grinding  work  between  centers,  it  is  essential 
to  set  the  headstock  to  zero;  otherwise  the  graduations  on 
the  end  of  the  table  will  not  show  the  angle  between  the  line 
of  motion  and  a line  joining  the  centers.  When  work  that 
is  attached  to  the  headstock  spindle  is  ground,  the  latter  is 
set  roughly  by  the  graduations  of  the  headstock,  but  the 
final  adjustment  is  gotten  by  setting  the  table  over. 

40.  The  adjustment  of  the  table  is  so  simple  in  all  grind- 
ing machines  that  in  case  the  work  shows  any  error  due  to 
alinement,  the  operator  finds  it  more  convenient  to  cure  the 
error  by  shifting  the  table  than  to  look  for  the  cause  of  the 
error  in  alinement. 


DRIVING  WORK  BETWEEN  CENTERS. 

41.  Work  ground  between  centers  is  driven,  as  in  lathe 
work,  by  a dog.  The  dog  used  should  be  as  light  as  possible, 
especially  for  slender  work,  and  should  be  well  balanced  in 
order  that  the  centrifugal  force  due  to  an  unbalanced  dog 
may  not  bend  the  work  during  grinding  and  thus  cause  poor 
results.  Most  grinding  machines  have  a pair  of  pins  set 
into  the  face  plate,  so  that  a straight-tailed  dog  having  two 
tails  can  be  used,  which  is  less  liable  to  produce  a bending 
stress  on  the  work  at  high  speeds  than  the  ordinary  bent- 
tailed dog.  Owing  to  the  fact  that  the  work  revolves  at  a 
slow  speed,  it  is  not  often  that  the  centrifugal  force  due  to 
an  unbalanced  dog  has  to  be  taken  into  account. 


EXTERNAL  GRINDING. 


METHODS  OF  GRINDING. 

42.-  Introduction. — A good  idea  of  the  kind  of  work 
that  can  be  done  in  a grinding  machine  can  be  obtained  by 
an  examination  of  the  several  examples  of  external  grind- 
ing that  are  given  below.  These  examples  will  serve  to 


GRINDING. 


17 


§ 19 


Fig. 


18 


GRINDING. 


§ 19 

show  how  the  machine  may  be  arranged  and  what  shape  of 
wheel  may  be  used  to  advantage.  They  may  be  profitably 
studied,  for  the  lessons  conveyed  by  them  will  serve  to  sug- 
gest ways  and  means  of  doing  work  different  from  that  shown. 

43.  Grinding  a Cylindrical  Rod. — Fig.  3 shows  one 
of  the  simplest  grinding  jobs  that  is  done,  which  is  the 
grinding  of  a cylindrical  rod  between  centers.  The  illustra- 
tion is  a top  view  of  a Landis  grinding  machine  where  the 
table  is  stationary  and  the  wheel  moves  past  the  work.’  The 
wheel  a is  set  at  right  angles  to  the  line  of  motion,  so  that 
its  cutting  surface  is  cylindrical.  In  order  to  grind  the 
work  cylindrical,  the  line  of  motion  of  the  wheel  must  be 
parallel  to  the  axis  of  rotation  of  the  work,  and  this  con- 
dition is  obtained  by  shifting  the  table  until  trial  shows  the 
work  to  be  cylindrical.  The  illustration  shows  the  manner 
of  driving  the  work  by  means  of  a dog  b having  two  tails 
that  balance  each  other,  though  in  practice  only  one  of  them 
is  in  contact  with  a driving  pin.  It  would  be  commercially 
impossible  to  grind  the  piece  shown  without  using  a number 
of  steady  rests,  but  they  are  not  shown,  as  they  would  only 
complicate  the  illustration. 

44.  Facing  a Bushing. — In  Fig.  4 is  shown  how  a 
bushing  may  be  faced  square.  The  bushing  c is  placed  on 


Fig.  4. 

a true-running  mandrel  that  is  put  between  the  centers  and 
is  driven  by  a dog.  In  order  that  the  grinding  wheel  may  pass 


§19 


GRINDING. 


19 


clear  over  the  end  of  the  bushing,  the  end  a of  the  mandrel 
should  be  turned  down  somewhat  smaller  than  the  part  fit- 
ting the  bushing;  the  latter  is  then  placed  on  the  mandrel 


fig.  5. 

so  that  the  face  that  is  to  be  ground  projects  somewhat 
from  the  shoulder  at  b.  Since  the  grinding  must  be  done 
by  the  side  of  the  wheel,  the  latter  should  be  recessed  as 
shown,  leaving  only  a narrow  surface  to  do  the  cutting. 


20 


GRINDING. 


§ 19 


Fig. 


§19 


GRINDING. 


21 


The  wheel  is  fed  against  the  face  in  the  direction  of  the  axis 
of  the  work;  this  will  generally  give  a better  face  than 
feeding  the  wheel  back  and  forth  across  the  face  of  the  work. 

45.  Grinding;  Conical  Work. — The  grinding  of  a 
short  frustum  of  a cone  is  shown  in  Fig.  5,  which  is  a top 
view  of  part  of  a Brown  & Sharpe  universal  machine.  The 
included  angle  being  beyond  that  attainable  by  swinging 
the  table  a , it  is  gotten  by  swiveling  the  lower  wheel  slide  b 
until  it  makes  the  required  angle  to  the  axis  of  rotation  of 
the  work,  the  table  a first  having  been  set  to  zero,  however, 
in  order  that  the  graduations  on  b may  give  a correct  indi- 
cation. In  this  case,  the  upper  wheel  slide  c is  set  at  right 
angles  to  b to  allow  a square-faced  wheel  to  be  used.  It 
will  be  observed  that  the  slides  b and  c form  what  may  be 
called  a compound  rest.  If  the  frustum  of  a cone  that  is 
being  ground  has  to  be  very  exact,  its  accuracy  will  most 
likely  be  tested  by  a gauge;  the  final  adjustment  for  the 
angle  is  then  made  by  swiveling  the  table  a by  means  of  the 
adjusting  screw  provided  for  the  purpose. 

46.  In  Fig.  6 is  shown  how  a piece  of  work  having  two 
different  conical  parts  may  be  ground,  where  one  of  the 
parts  is  within  the  range  of  angles  that  can  be  obtained  by 
swiveling  the  table  a.  Thus,  the  conical  part  b is  ground 
with  the  table  set  over,  while  the  conical  part  c is  ground 
by  setting  the  lower  wheel  slide  d to  an  angle  to  suit  the 
required  angle.  It  is  to  be  observed  that  the  graduations 
on  d will  not  indicate  the  angle  of  c , since  the  table  a is  not 
at  zero.  One  edge  of  the  grinding  wheel  is  beveled  to  suit 
the  conical  part  c.  The  wheel  is  adjusted  for  depth  of  cut 
by  moving  it  along  the  upper  wheel  slide  e. 

When  a number  of  duplicate  pieces  like  that  shown  in 
Fig.  6 are  to  be  ground,  the  sensitive  adjustment  of  the 
table  can  only  be  used  for  the  conical  part  b.  The  final 
adjustment  for  c must  be  gotten  by  shifting  the  lower  slide  d. 
As  long  a piece  as  the  one  shown  could  not  be  ground  with- 
out the  use  of  steady  rests. 


22 


GRINDING. 


19 


47.  Grinding  Close  to  Shoulder. — An  example  of 
grinding  a shaft  close  to  a large  shoulder  is  shown  in  Fig.  7. 
In  this  case,  the  ordinary  flat  wheel  cannot  be  used,  since 
the  nut  and  the  washers  used  for  fastening  it  to  the  spindle 
will  come  in  contact  with  the  shoulder  of  the  work  while  the 
wheel  is  yet  some  distance  from  the  shoulder.  For  this 


Fig.  7. 


reason,  the  dished  wheel  shown  in  the  illustration  is  used. 
It  is  not  advisable  to  use  such  a wheel  for  grinding  the 
face  a of  the  shoulder,  owing  to  the  large  grinding  surface 
that  will  be  in  contact  with  the  work.  The  wheel  cannot 
clear  itself  of  the  particles  of  metal,  and  if  the  shoulder 
requires  grinding,  it  is  better  to  recess  the  wheel  in  order 
to  narrow  the  grinding  surface. 

48.  Grinding  a Caliper  Gauge.  — The  grinding  of 
a caliper  gauge  is  shown  in  Fig,  8,  the  illustration  being  a 


§19 


GRINDING. 


23 


partial  top  view  of  a Landis  grinding  machine.  The  gauge  a 
is  damped  to  the  table  b}  which  has  been  set  to  zero.  The 
wheel  slide  c is  set  at  right  angles  to  the  table  and  a wheel 


recessed  as  shown  is  used.  The  grinding  is  done  by  moving 
the  wheel  slide  rapidly  back  and  forth  across  the  caliper  face. 
A rather  soft  wheel  should  be  used  for  this  kind  of  grinding. 

It  will  be  noticed  that  in  producing  the  flat  face  shown  in 
Fig.  4,  the  wheel  was  not  moved  across  the  work,  while  in 
C.  S.  III.— 7 


24 


GRINDING. 


§ 19 

the  present  case  it  is  very  necessary  to  move  the  wheel 
across  the  face  of  the  work.  The  reason  for  this  is  that  in 
the  first  case  the  work  c was  revolving,  while  in  Fig.  8 the 
gauge  a is  standing  still. 

49.  Truing  Centers. — Fig.  9 shows  how  the  centers* 
may  be  trued  in  a universal  grinding  machine  by  swinging 
the  headstock  around  to  make  an  angle  of  30  degrees  with 
the  line  of  motion  in  order  that  the  centers  may  be  ground 


Fig.  9. 


to  the  American  standard  angle  of  60  degrees.  In  all  mod- 
ern grinding  machines,  the  headstock  center  and  tailstock 
center  interchange,  so  that  both  centers  may  be  trued  in 
the  headstock  spindle.  In  plain  grinding  machines,  where 
the-  headstock  cannot  be  swiveled,  the  centers  are  trued  by 
means  of  a special  fixture  that  is  nothing  but  a supple- 
mentary headstock  that  is  removed  from  the  machine  after 
the  centers  are  ground.  Obviously  the  spindle  must  rotate 
for  center  grinding. 

50.  Chuck  Work  and  Face-Plate  Work.  — The 

manner  of  using  a universal  grinding  machine  for  chuck 
work  and  face-plate  work  is  shown  in  Fig.  10.  When  the 
work  is  to  be  ground  to  a plane  surface,  the  headstock  is 
placed  exactly  at  right  angles  to  the  line  of  motion  of  the 


§ 19 


GRINDING. 


25 


table  or  grinding  wheel,  the  table  first  having  been  set  to 
zero.  The  final  adjustment  is  obtained  by  means  of  the  sensi- 
tive adjustment  with  which  the  table  is  supplied,  taking  trial 


cuts  over  the  work  and  testing  it  with  a straightedge.  For 
conical  work  the  headstock  is  swiveled  to  the  required  angle. 

51.  Special  Chucks. — Thin  saws,  milling  cutters,  and 
similar  work  that  either  cannot  very  readily  be  held  in  the 
chuck  Or  that  cannot  be  attached  to  a face  plate  because 
the  clamping  devices  are  in  the  way  of  the  grinding  wheel, 
can  often  be  successfully  held  for  grinding  by  means  of  the 
special  chuck  shown  in  Fig.  11,  the  use  of  which  presupposes 
that  the  work  has  a fair-sized  round  hole  whose  axis  is  at 
right  angles  to  the  face  that  is  to  be  ground.  A face  plate  a 


26 


GRINDING. 


§ 19 

is  screwed  to  the  headstock  spindle.  A sleeve  b that  is 
threaded  on  the  inside  to  fit  the  screws  c and  d is  nicely 
fitted  to  the  central  hole  of  the  face  plate;  this  sleeve  is 
axially  movable  and  is  kept  from  turning  by  a pin  that 


works  in  a longitudinal  slot  of  the  face  plate.  The  front 
end  of  the  sleeve  b is  arranged  to  take  the  shank  of  the 
bushing  e,  the  projecting  part  of  which  is  fitted  to  the  hole 
in  the  work.  The  bushing  e is  split  so  that  it  can  be  ex- 
panded to  grip  the  work  tightly  by  turning  the  conically 
headed  screw  c.  When  this  has  been  done,  the  work  is  drawn 
against  the  face  plate  by  turning  the  small  hand  wheel  f, 
which  is  keyed  to  the  screw  d.  A separate  bushing  will  be 
required  for  each  size  of  hole. 


THE  SET  WHEEL. 

52.  When  a large  number  of  duplicate  pieces  of  simple 
form  are  to  be  ground,  grinding-machine  operators  usually 
employ  the  so-called  set-wheel  method  of  grinding.  In 
this  method,  all  the  pieces  are  first  roughed  out  to  within 
a small  limit  of  the  finished  size,  say  .001  inch,  and  then  all 
are  finished.  In  using  this  method,  the  operator  first  sets 


GRINDING. 


27 


§ 19 

the  grinding  wheel,  by  trial,  to  the  roughing  size,  and  then, 
without  moving  the  wheel  slide,  grinds  all  the  pieces  to 
the  roughing  size,  measuring  the  work  from  time  to  time 
and  moving  the  wheel  toward  the  work  to  make  up  for 
the  wear  of  the  wheel.  When  all  the  pieces  have  been 
roughed  out,  the  wheel  is  set,  by  trial,  to  grind  the  work  to 
the  finished  size  and  piece  after  piece  is  put  into  the  machine 
and  finished  without  disturbing  the  setting  of  the  wheel, 
except  to  compensate  for  the  wear. 

53.  For  the  set-wheel  method,  a wheel  should  be  selected 
that  will  not  wear  very  rapidly;  and  after  all  the  pieces  are 
roughed  out,  the  wheel  should  be  carefully  trued  by  means 
of  a diamond  tool.  It  will  then  produce  a smooth  and  even 
surface  on  the  light  finishing  cut,  although  the  surfaces 
produced  on  the  heavy  roughing  cuts  may  have  been  rather 
coarse. 


STEADYING  WORK. 

54.  Purpose  of  Rests. — When  grinding  long  and 
comparatively  slender  work,  it  is  necessary,  just  as  in  lathe 
work,  to  use  some  means  to  prevent  the  deflection  of  the 
work,  owing  either  to  its  own  weight  or  to  the  pressure  of 
the  cut.  For  this  purpose  a follow  rest  may  be  used,  or 
a number  of  steady  rests  may  be  applied  to  the  work. 

55.  Benefits. — The  benefits  derived  from  a proper  ap- 
plication of  rests  to  the  work  are:  the  production  of  a better  k 
quality  of  work;  the  possibility  of  taking  heavier  cuts  and 
the  using  of  a greater  speed  and  rate  of  feed  ; and,  finally,  an 
increase  in  the  sizing  power  of  the  wheel.  The  term  sizing 
power  refers  to  the  ability  of  the  wheel  to  maintain  its  size 
for  a fair  length  of  time,  which  enables  it  to  duplicate  a 
large  number  of  pieces  without  any  movement  of  the  wheel 
slide. 

56.  Classification  of  Rests. — The  rapidly  increasing 
use  and  the  consequent  development  of  the  grinding  ma- 
chine have  led  to  a great  number  of  designs  of  rests  for  the 
steadying  of  work  while  grinding.  The  different  designs 


28  GRINDING.  § 19 

easily  divide  into  two  general  classes,  which  may  be  called 
follow  rests  and  fixed  rests. 

57.  A follow  rest  may  be  defined  as  a rest  that  main- 
tains its  position  in  relation  to  the  wheel ; i.  e.,  is  stationary 
in  respect  to  it  throughout  the  cut.  Such  a rest  is"  only 
adapted  to  cylindrical  work,  and  for  a long  time  was  the 
only  rest  supplied  to  grinding  machines. 

58.  A fixed  rest,  or  back  rest,  is  a rest  that  is  fast- 
ened to  the  table  of  the  grinding  machine,  and  which, 
consequently,  remains  fixed  with  respect  to  the  work.  Such 
a rest  is  conceded  by  most  operators  to  be  superior  to  a 
follow  rest,  even  for  straight  work.  The  fixed  rest  can  also 
be  used  on  tapered  work  or  work  having  different  diameters. 
Fixed  rests  may  be  divided  into  two  subclasses,  which  are 
called  rigid  fixed  rests  and  flexible  fixed  rests. 


59.  Construction  of  Rests. — A rigid  fixed  rest  is 

shown  in  Fig.  12,  which  also  shows  its  application  to  the 


work  in  a Landis  machine.  The  frame  a of  the  rest  is 
rigidly  bolted  to  the  table;  a swinging  arm  b is  fulcrumed 
to  the  upper  part  of  the  frame  and  can  be  moved  slightly  by 
means  of  the  adjusting  screw  c An  adjustable  cylindrical 
plug  d is  carried  by  the  swinging  lever,  to  which  it  can  be 
clamped  by  a setscrew.  This  plug  is  placed  in  contact  with 


GRINDING. 


29 


§ 19 

the  bottom  of  the  work,  the  sensitive  adjustment  being 
obtained  by  the  screw  c,  and  the  rough  adjustment,  for  the 
diameter  of  the  work,  by  sliding  the  plug  in  the  lever.  A 
setscrew  e is  used  for  steadying  the  work  sidewise. 

60.  When  using  a rigid  rest,  it  is  not  necessary  for  the 
operator  to  spot  the  work  at  the  place  where  the  rest  is 
applied.  The  rest  is  simply  applied  to  the  work  and  grind- 
ing commenced.  The  emery  wheel  will  cut  more  from  the 
high  side,  even  though  the  rest  may  appear  to  hold  the  work 
so  that  it  runs  true,  and  the  work  will  finally  come  out 
round  and  straight.  Care  must  be  exercised  in  adjusting 
the  parts  of  a rigid  rest,  as  d and  for  a very  little  pressure 
will  deflect  a slender  bar,  and  if  the  rest  is  set  up  too  hard 
the  work  may  be  ground  small  in  the  middle.  As  the 
diameter  of  the  work  is  reduced,  a rigid  rest  must  be  re- 
adjusted. 

61.  Flexible  fixed  rests  are  made  in  various  ways; 
the  simplest  form  is  the  so-called  spring  rest  shown  in 
Fig.  13.  The  frames  is 
fastened  to  the  table  of 
the  machine;  it  has  a 
rectangular  recess  at 
the  top  into  which  the 
rectangular  shank  of 
the  shoe  b is  so  fitted  as 
to  move  easily.  The 
end  of  the  shoe  that 
bears  against  the  work  is  curved  to  suit  the  diameter  of  it; 
the  rear  end  of  t lie  shoe  is  acted  upon  by  a helical  spring  c 
whose  tension  can  be  adjusted  by  means  of  the  thumb- 
screw d.  The  shoe  should  be  made  of  some  soft  material, 
as  brass,  babbitt,  or  wood.  This  kind  of  a rest  reduces  or 
eliminates  the  vibration  of  the  work  by  reason  of  the  inertia 
of  the  shoe  and  the  tension  of  the  spring  c ; it  is  open  to  the 
objection,  however,  that  too  great  a tension  of  the  spring 
will  cause  the  work  to  be  bent.  On  the  other  hand,  the 
spring  will  cause  the  shoe  to  follow  up  automatically  any 


30 


GRINDING. 


§ 19 


reasonable  reduction  in  the  diameter  of  the  work.  The  shoe 
should  never  be  made  of  any  hard  material,  as  it  should  wear 
rapidly  to  a good  fit,  on  account  of  the  fact  that  the  value 
of  the  shoe  in  absorbing  vibrations  depends  largely  on  the 
degree  of  its  contact  with  the  work. 


G2.  The  universal  back  rest  supplied  by  the  Brown 
& Sharpe  Manufacturing  Company  with  their  plain  grinding 


machines  is  shown  in  Fig.  14.  The  back  rest  for  the  uni- 
versal machines  works  on  the  same  principle,  but  is  con- 
structed quite  differently.  The  frame  a is  clamped  to  the 
table  of  the  machine  by  turning  the  nut  a' . A swinging 
lever  b is  pivoted  to  the  frame  at  c\  a spring  d , whose  tension 
can  be  adjusted  by  the  thumbnut  e,  tends  to  force  the  upper 
end  of  b toward  the  work.  The  extent  to  which  the  lever 


§ 19 


GRINDING. 


31 


can  move  toward  the  work  is  regulated  by  the  thumbscrew  fy 
whose  end,  by  coming  in  contact  with  a shoulder  g of  the 
frame,  limits  the  motion  of  b.  The  shoe-carrying  frame  h is 
hinged  to  the  upper  end  of  the  lever  b,  and  the  front  end  of  h 
rests  on  a part  of  the  frame  a.  This  construction  allows  the 
frame  h to  move  toward  the  work  to  the  extent  permitted  by 
the  position  of  the  screw  fy  but  does  not  permit  the  front  end 
of  li  to  drop.  The  shoe  i has  trunnions,  as  i\  which  rest  in 
V notches  formed  at  the  front  end  of  h.  The  shoe  is  held 
against  the  work  by  a helical  spring  k,  whose  tension  is  ad- 
justed by  the  thumbnut  /.  The  spring  k bears  against  the 
movable  nut  in,  which  carries  the  adjusting  screw  n,  the  end 
of  which  bears  against  the  shoe.  From  the  construction  it 
follows  that  the  action  of  the  spring  k causes  a rotation 
of  the  shoe  i about  i\  thus  tending  to  draw  the  part  ix  of 
the  shoe  against  the  work.  The  screw  n passes  through  a 
clearance  hole  in  the  thumbnut  /,  and  its  axial  motion 
under  the  action  of  the  spring  k is  limited  by  the  lower  face 
of  the  nut  in  coming  against  a shoulder  o of  the  shoe- 
carrying frame. 

63.  From  the  construction  of  the  device  it  follows  that 
the  part  i2  of  the  shoe  is  held  against  the  work  by  the 
spring  d,  while  z,  is  held  against  the  work  by  the  spring  k. 
It  also  follows  from  the  construction  that  the  pressure  of 
the  shoe  against  the  work  can  be  arrested  at  a predetermined 
diameter  by  a proper  adjustment  of  in  and  f in  respect  to 
the  shoulders  g and  o.  If  these  adjustments  are  properly 
made,  it  is  impossible  for  the  springs  to  bend  the  work. 
Different  sizes  of  shoes  will  be  required  for  different  diam- 
eters of  the  work;  since  the  shoes  are  removed  by  simply 
lifting  them  out  of  the  V’s  in  the  frame  h , they  are  readily 
changed. 

64.  Since  the  shoe  is  operated  by  spring  pressure  in  two 
directions  at  right  angles  to  each  other,  it  can  yield  to  suit 
the  inequalities  of  unground  work,  and,  hence,  there  is  no 
necessity  of  grinding  the  work  to  run  true  at  the  place  where 
the  rest  is  applied,  prior  to  the  application. 


‘SI  ‘Old 


GRINDING. 


33 


§ 19 

65.  Application  of  Universal  Rests. — Fig.  15  is  a 
perspective  view  of  a plain  grinding  machine,  showing  how 
the  universal  rests  are  applied  to  a long  piece  of  work.  In 
order  to  steady  the  work  f,  a number  of  rests,  as  a , b , c , d , 
and  <?,  are  used,  which  are  placed  from  G to  8 diameters  of  the 
work  apart.  Each  rest  is  independently  adjusted  to  properly 
bear  against  the  work.  This  illustration  incidentally  shows 
on  the  footstock  a truing  device  g for  holding  a diamond- 
pointed  tool.  As  clearly  shown,  the  tool  is  held  in  place  by 
a small  thumbscrew;  in  use  the  depth  of  cut  is  obtained  by 
moving  the  wheel  slide,  and  the  grinding  wheel  is  moved 
back  and  forth  past  the  tool. 

66.  Absorption  of  Vibration. — When  comparatively 
stiff  work  that  is  being  ground  without  a rest  commences  to 
vibrate,  as  occurs  occasionally,  the  vibrations  can  some- 
times be  absorbed  by  holding  a block  of  wood  against  the 
work  by  hand,  resting  one  end  of  the  block  on  the  table. 
This  is  only  a makeshift  to  be  used  where  single  pieces  are 
being  ground.  In  doing  commercial  work,  a rest  should 
always  be  used.  Whenever  a piece  of  work  or  a wheel  com- 
mences to  vibrate,  the  cause  should  be  looked  up  and  the 
proper  remedy  applied.  The  vibration  may  be  caused  by  a 
glazed  wheel,  improper  speed  of  wheel  or  work,  or  irregu- 
larities in  the  stock. 

67.  Special  Rests. — Where  a large  number  of  dupli- 
cate pieces  are  to  be  ground,  special  rests  can  often  be  ad- 
vantageously used.  These  rests  must  usually  be  of  the 
fixed-rest  type,  and  may  be  rigid  rests  or  spring  rests. 
Their  design  rarely  presents  any  difficulties,  as  they  are  gen- 
erally but  simple  modifications  of  the  rests  here  described, 
the  modification  having  been  made  necessary  by  the  shape 
of  the  work. 


POOLE  METHOD  OF  CYLINDRICAL  GRINDING. 

68.  As  is  well  known,  a round  bar  may  show  under 
very  refined  measurements  as  being  exactly  round  and  of 
uniform  diameter,  and  may  yet  be  far  from  straight;  that 


34 


GRINDING. 


Fig.  16. 


§19 


GRINDING. 


35 


is,  it  may  be  far  from  a true  cylinder.  In  all  ordinary 
grinding  machines,  the  straightness  of  the  work  depends 
primarily  on  the  straightness  of  the  guiding  ways  that  de- 
termine the  line  of  motion  of  the  wheel  or  the  work,  and 
while  the  work  may  be  round  in  spite  of  a want  of  truth  of 
the  guiding  ways,  any  error  in  them  is  bound  to  produce 
work  that  is  not  straight.  While  it  is  not  a very  difficult 
matter  to  produce  straight  guiding  ways  in  small  grinding 
machines  intended  for  comparatively  light  work,  the  prob- 
lem becomes  more  difficult  when  a machine  suitable  for 
the  grinding  of  such  work  as  the  calender  rolls  used  in  paper 
making  is  to  be  constructed.  Such  rolls  are  quite  large  and 
must  be  exceedingly  straight  and  uniform  in  diameter;  on 
account  of  the  difficulty  of  making  the  guiding  ways  suffi- 
ciently true,  Mr.  J.  Morton  Poole  devised  a special  method 
of  grinding  that  largely  overcomes  any  reasonable  error 
that  would  be  induced  by  want  of  straightness  of  the  guid- 
ing ways.  In  the  Poole  method  of  grinding,  the  periphery 
of  the  grinding  wheel  is  kept  at  a constant  distance  from 
the  axis  of  rotation  of  the  work,  not  by  the  straightness  of 
the  guiding  ways,  but  by  gravity,  as  will  become  apparent 
when  the  construction  of  the  machine  is  studied. 

69.  Fig.  16  is  a perspective  view  of  the  machine,  which 
in  some  respects  resembles  a lathe  with  the  tailstock  left  off. 
The  carriage  a that  carries  the  grinding  wheels  is  mounted 
on  V’s,  along  which  it  can  be  traversed.  The  roll  that  is  to 
be  finished  has  its  two  journals  ground  perfectly  true  and 
these  journals  are  placed  in  the  jaws  of  the  steady  rests  b 
and  c.  The  jaws  of  these  rests  are  both  the  same  height 
above  the  guiding  ways.  The  work  is  driven  from  the  head- 
stock  spindle  d by  means  of  a flexible  connection,  in  order 
that  any  want  of  alinement  between  the  axes  of  rotation  of 
the  work  and  the  spindle  may  not  disturb  the  former  during 
grinding.  Two  grinding  wheels  are  used  on  opposite  sides 
of  the  work;  each  grinding  wheel  is  mounted  on  its  own 
wheel  slide.  The  two  slides  work  in  a heavy  casting  e that 
forms  their  base;  this  casting  is  supported  by  four  links, 


3G 


GRINDING. 


§19 

as  f,  f,  from  the  top  of  the  carriage  by  means  of  knife-edge 
bearings.  This  construction  allows  the  grinding  wheels  to 
swing  freely  in  a direction  at  right  angles  to  the  axis  of  rota- 
tion of  the  work,  and  the  wheels  will  obviously  be  at  rest 
when  the  center  of  gravity  of  the  whole  swinging  part  occu- 
pies its  lowest  position. 

70.  The  distance  that  the  grinding  wheels  are  apart 
during  each  cut  being  constant,  it  follows  that  the  roll  being 
ground  will  be  of  uniform  diameter  throughout,  neglect- 
ing here  the  wear  of  the  grinding  wheels  which  will  be  ex- 
ceedingly small  during  a light  finishing  cut.  Now,  as  stated 
in  Art.  08,  a bar  may  be  apparently  round  and  of  uniform 
diameter  without  being  straight.  Any  one  who  is  in  doubt 
about  this  statement  is  advised  to  take  a straight  piece  of 
drill  rod,  which,  as  supplied  by  manufacturers,  is  quite  round 
and  exceedingly  uniform  in  diameter,  and  to  bend  it  slightly. 
It  will  then  be  found  that  with  a reasonable  amount  of  bend- 
ing the  piece  will  caliper  the  same  throughout  its  length. 
While  there  is  no  doubt  but  that  the  diameter  and  also  the 
roundness  of  the  piece  are  changed  by  the  bending,  the  fact 
remains  that  the  change  is  so  slight,  when  the  bend  is  not 
excessive,  as  to  be  insensible. 

71.  Assume  that  the  roll  being  ground  is  not  exactly 
straight.  Then,  when  revolved  in  the  steady  rests  b and  c, 
it  will  run  out  of  true,  and  the  high  side  coming  toward 
one  of  the  emery  wheels  will  tend  to  push  over  the  swinging 
frame.  This  tendency  is  resisted  by  the  weight  of  the 
swinging  frame,  and,  consequently,  there  is  a pressure,  de- 
pendent on  the  amount  that  the  roll  runs  out  of  true,  that 
causes  the  wheels  to  alternately  cut  away  the  high  side  until 
the  center  of  gravity  of  the  swinging  frame  is  in  its  lowest 
position  again,  when  the  wheel  ceases  to  cut.  It  will  be 
understood  that  the  frame  swings  back  and  forth  as  the 
high  side  of  the  revolving  roll  engages  one  or  the  other  of 
the  two  grinding  wheels.  By  repeated  passages  of  the  car- 
riage along  the  bed,  the  roll  is  finally  so  ground  as  to  run 
perfectly  true;  and  as  the  fixed  distance  between  the  wheels 


GRINDING. 


37 


§ 19 

insures  a uniform  diameter,  the  finished  roll  becomes  a very 
close  approach  to  a perfect  cylinder,  independently  of  the 
truth  of  the  guiding  ways.  In  practice  the  operator  takes 
most  or  all  of  the  swing  out  of  the  carriage  while  roughing 
the  roll.  On  the  whole,  this  is  a rather  slow  process,  though 
it  produces  very  good  work.  Some  classes  of  rolls  have  to 
be  ground  large  or  small  in  the  middle.  This  may  be  done 
by  raising  or  lowering  the  swinging  carriage  at  the  proper 
points,  so  as  to  bring  the  wheels  above  or  below  the  center 
of  the  roll.  As  soon  as  the  wheels  are  removed  from  the 
center  of  the  work  they  will  grind  large. 


INTERNAL  GRINDING. 


INTRODUCTION. 

72.  Internal  grinding  presents  problems  of  a prac- 
tical nature  that  differ  somewhat  from  those  encountered  in 
external  grinding;  since  a knowledge  of  the  causes  of  these 
problems  is  essential  to  their  partial  or  entire  solution,  they 
are  here  briefly  explained. 

73.  Influence  of  Pressure. — -In  internal  grinding  the 
truth  of  the  surfaces,  at  least  as  far  as  the  grinding  itself  is 
concerned,  depends  primarily  on  the  amount  of  pressure 
caused  by  the  grinding  operation  As  in  the  case  of  ex- 
ternal work,  this  pressure  tends  to  disturb  the  position  of 
the  axes  of  rotation  of  the  work  and  the  grinding  wheel; 
since  the  amount  of  disturbance  depends  directly  on  the 
pressure,  it  follows  that  a reduction  of  it  to  the  lowest  limit 
attainable  with  a given  set  of  conditions  causes  a corre- 
sponding reduction  of  errors  and  a consequent  increase  in 
the  truth  of  the  work. 

7-4.  Pressure  Greater  Titan  in  External  Grind- 
ing.— ’The  pressure  required  to  make  the  wheel  cut  is 
always  greater  in  internal  grinding  than  in  external  grinding, 
especially  when  the  hole  that  is  being  ground  is  small.  The 


38 


GRINDING. 


19 


reason  of  this  is  the  more  intimate  contact  of  the  grinding 
wheel  with  the  surface  of  the  work ; the  extent  of  this  contact 

will  become  apparent 
when  a grinding  wheel 
but  slightly  smaller 
than  the  hole  is  em- 
ployed. It  may  be 
stated  that  for  equal 
depths  *of  cut,  equal 
diameters  of  wheels, 
equal  diameters  of  the 
work,  and  equal  widths 
of  the  wheels,  the  ex- 
tent of  the  surface  of 
the  wheel  in  contact 
with  the  work  will  al- 
ways be  greater  in  in- 
ternal grinding  than 
in  external  grinding. 
This  is  shown  in 
Fig.  17,  where  a cyl- 
inder a and  a cylin- 
drical ring  b having 
the  same  diameter  of  the  surface  to  be  ground,  are  illus- 
trated. The  grinding  wheels  c and  d have  the  same  diam- 
eter, and  both  are  set  for  the  same  depth  of  cut.  It  is 
plainly  seen  that  the  surface  with  which  the  wheel  is  in 
contact  is  greatest  in  internal  grinding,  and  it  can  be  readily 
understood  that  the  pressure  of  the  cutting  operation  will 
be  greater  than  in  external  grinding.  From  these  facts  the 
conclusion  may  readily  be  drawn  that  in  order  to  reduce  the 
pressure  of  the  cut,  the  depth  should  be  much  less  in  in- 
ternal than  in  external  grinding. 


75.  Best  Cutting  Speed  Cannot  Be  Obtained.- — 

The  grinding  wheel  obviously  must  be  smaller  than  the  hole 
in  which  it  is  to  be  used,  and  a very  small  hole  requires  a very 
small  wheel.  In  order  to  obtain  the  best  cutting  speed,  the 


19 


GRINDING. 


39 


wheel  would  have  to  be  run  at  a very  high  number  of  revo- 
lutions per  minute.  While  it  has  been  found  possible  in 
practice  to  run  a very  small  grinding  spindle  of  exquisite 
workmanship  at  the  enormous  rate  of  75,000  revolutions  per 
minute,  even  this  high  rate  of  speed  falls  very  much  short 
of  giving  the  best  surface  speed  to  the  grinding  wheel.  At 
present  the  art  of  making  a spindle  and  bearings  for  it  to  run 
at  the  number  of  revolutions  that  would  produce  a proper 
surface  speed  has  not  progressed  far  enough  to  allow  this  to 
be  done,  at  least  for  small  holes. 

7 6.  When  a grinding  wheel  is  run  at  a surface  speed 
below  its  best  cutting  speed,  more  pressure  will  be  required 
to  make  it  cut,  but  as  the  required  pressure  is  less  with  a 
soft  wheel  than  with  a hard  one,  it  follows  that  a softer 
wheel  should  be  used  whenever  circumstances  prevent  the 
attainment  of  a proper  surface  speed.  Since  the  condition 
just  named  exists  usually  in  internal  grinding,  it  follows  that 
much  softer  wheels  should  be  used  than  for  external  grind- 
ing, in  order  to  reduce  the  pressure. 

77.  Considerations  Affecting  Stiffness  of  Spin- 
dle.— In  the  case  of  external  grinding,  the  spindle  that 
carries  the  grinding  wheel  can  always  be  made  as  stiff  as 
may  be  desired;  in  the  case  of  internal  grinding,  however, 
the  size  of  the  hole  that  is  to  be  ground  determines  the 
maximum  diameter  of  the  spindle.  Then,  if  the  hole  is 
small  and  deep,  the  spindle  must  be  correspondingly  small 
and  slender;  consequently,  it  is  bound  to  yield  to  a sensible 
extent  under  a very  moderate  pressure.  From  the  state- 
ments just  made,  it  will  be  apparent  that  in  order  to  reduce 
the  deflection  of  the  spindle,  it  should  be  as  large  as  circum- 
stances will  permit,  and  be  supported  close  to  the  grinding 
wheel. 

78.  In  the  earliest  designs  of  internal-grinding  fixtures, 
a spindle  of  as  large  diameter  as  possible  was  employed,  and 
the  distance  from  the  wheel  to  the  nearest  support  was 
at  least  equal  to  the  depth  of  hole  to  be  ground.  It  was 
soon  found,  however,  that  while  the  requisite  stiffness  was 

C.  S.  III.— 8 


40 


GRINDING. 


§ 19 

obtained,  another  serious  error  not  previously  thought  of  was 
introduced.  This  error  was  due  to  the  looseness  of  the 
spindle  in  its  bearings,  which  is  necessary  for  free  running, 
but  which  shows  much  greater  at  the  end  of  the  spindle  by 
reason  of  the  long  distance  between  the  wheel  and  the  near- 
est bearing.  The  consequent  wabbling  of  the  wheel  caused 
it  to  follow  the  imperfections  of  the  hole  being  ground  and 
precluded  the  grinding  of  a true  hole. 

79.  When  the  spindle  is  made  as  large  as  the  hole  will 
permit,  it  is  obviously  impossible  to  place  a bearing  adjacent 
to  the  emery  wheel.  Hence,  in  order  to  place  a bearing  in 
that  position,  the  diameter  of  the  spindle  must  be  cut  down ; 
and  to  give  the  requisite  stiffness,  the  bearing  must  be  of 
such  a form  that  it  will  make  up  for  the  reduced  diameter 
of  the  spindle.  This  consideration  requires  the  bearing  to 
be  a cylindrical  shell  carrying  the  spindle  inside  and  hav- 
ing its  outside  diameter  slightly  smaller  than  the  diameter 
of  the  smallest  hole  in  which  the  internal-grinding  fixture 
is  to  be  used.  Then,  if  the  bearing  is  directly  back  of  the 
grinding  wheel,  its  possible  side  movement  will  exceed  but 
slightly  the  side  movement  (the  looseness)  of  the  spindle  in 
its  bearing. 

80.  Construction  of  an  Internal-Grinding  Fix- 
ture.— The  Brown  & Sharpe  Manufacturing  Company  was 


the  first  firm  to  construct  an  internal-grinding  fixture  along 
the  lines  mentioned  in  Art.  79.  This  fixture  is  shown  in 


19 


GRINDING. 


41 


section  in  Fig.  18.  The  grinding  wheel  a is  carried  by  the 
spindle  b , which  has  a long  journal  working  in  a split-bronze 
bearing  c.  The  spindle  is  held  in  place  lengthwise  by  the 
collar  d,  which  bears  against  the  end  of  c on  one  side,  and  on 
the  other  side  bears  against  the  end  of  the  tube  e.  The  out- 
side of  the  bearing  c is  tapered  and  fits  the  tapering  bore  of 
the  supporting  shell  f.  The  wear  of  the  bearing  is  taken  up 
by  screwing  the  tube  e into  the  shell,  thus  causing  the  bear- 
ing to  close.  The  tube  e is  then  slightly  unscrewed  to  give 


the  collar  d a free  running  fit.  The  end  of  the  spindle  is 
splined  and  fits  loosely  in  a central  hole  of  the  driving 
shaft  g,  which  carries  the  driving  pulley  h.  Two  pins  i and  j 
engage  the  splined  end  of  the  spindle  and  cause  it  to  turn 
with  the  driving  shaft.  The  outer  shell  f and  the  end  of 
the  tube  e are  sliding  fits  in  the  bearings  k and  /,  and  f can 
be  clamped  to  k.  This  construction  permits  the  wheel  a to 


42  GRINDING.  § 19 

be  brought  somewhat  closer  to  the  bearing  k for  shallow 
holes. 

81.  Driving  the  Spindle. — The  method  of  driving 
the  spindle  for  internal  grinding  is  shown  in  Fig.  19.  The 
grinding  wheel  is  removed  from  the  wheel  stand  a and  a 
driving  pulley  b is  put  in  its  place.  The  wheel  stand  a is 
then  reversed,  so  that  it  occupies  the  position  shown  in 
the  illustration.  The  pulley  c is  now  belted  to  the  drum 
overhead.  The  internal-grinding  fixture  d is  bolted  to  the 
wheel  slide;  its  spindle  is  then  driven  by  belting  its  driving 
pulley  e to  the  pulley  b. 


METHODS  OF  GRINDING. 

82.  Grinding  Conical  Work. — Fig.  19  shows  how 
the  universal  machine  is  used  for  grinding  a hole  having  a 
double  taper;  i.  e.,  whose  surfaces  form  frustums  of  two 
different  cones.  The  table  f is  swung  around  to  grind  the 
smaller  taper,  and  the  wheel  slide  g is  set  over  in  order  to 
grind  the  larger  taper. 

When  the  machine  has  a swivel  headstock,  one  taper 
might  be  ground  by  setting  over  the  headstock,  leaving  the 
table  at  zero.  The  other  taper  is  then  ground  by  setting 
over  the  wheel  slide,  or  changing  the  setting  of  the  head- 
stock. 

83.  Fig.  20  shows  how  a tapering  hole  in  the  end  of  a 
spindle  may  be  ground  to  run  true  with  the  outside.  One 
end  of  the  spindle  is  held  in  the  independent  jaw  chuck  a , 
while  the  other  end  is  run  in  the  center  rest  b.  For  test- 
ing the  truth  of  the  end  of  the  spindle  that  is  held  in  the 
chuck,  a sensitive  indicator  should  be  used,  the  operator 
revolving  the  headstock  spindle  by  hand  and  truing  the 
work  until  the  indicator  shows  it  to  run  dead  true.  The 
center  rest  insures  that  the  other  end  of  the  spindle  runs 
true.  The  proper  taper  is  obtained  by  setting  over  the 
table.  When  adjusting  the  center  rest,  great  care  must  be 
taken  that  the  work  is  not  thrown  out  of  alinement  with  the 


GRINDING. 


43 


§ 19 

axis  of  rotation  of  the  headstock  spindle,  for  if  this  is  done, 
the  jaws  of  the  chuck  will  badly  mar  the  end  of  the  work, 
and  besides  the  work  is  likely  to  creep  slowly  forwards  in  the 
direction  of  its  length  during  the  grinding.  The  jaws  of 


fig  co 


the  center  rest  should  touch  the  outside  of  the  work  just 
enough  to  prevent  any  shaking.  If  they  are  set  up  too 
tight,  the  work  will  heat  very  rapidly,  and  since  it  expands 


GRINDING. 


44 


19 


with  the  heat,  it  will  cause  a still  greater  pressure  on  the 
ends  of  the  jaws,  which  may  score  the  work. 


84.  Chucks. — -Universal  chucks  are  not  to  be  recom- 
mended for  grinding  machines,  because  they  will  not  hold 
the  work  true  enough  for  the  purpose.  Independent  jaw 
chucks  are  preferable  in  every  respect,  since  they  not  only 
allow  the  work  to  be  trued  carefully,  but,  also,  frequently 
permit  hardened  work  having  a small  grinding  allowance  to 
be  trued  to  suit  the  warping  induced  by  the  hardening  proc- 
ess. If  such  work  is  held  in  a universal  chuck,  it  will  often 
be  impossible  to  finish  it  to  size  with  the  given  grinding 
allowance,  owing  to  the  lack  of  truth  in  the  chuck  itself 
and  the  inability  to  true  the  work  to  suit  the  warping. 

85.  It  sometimes  occurs  that  a shell  or  thin  cylinder 
cannot  be  trued  sufficiently  in  the  ordinary  independent 

jaw  chuck.  In  that  case  a so-called 
bell  chuck  may  be  used.  This 
form  has  the  advantage  over  the 
jawed  chuck  in  that  it  allows  both 
ends  of  the  work  to  be  trued  inde- 
pendently of  each  other.  Such  a 
chuck  is  shown  in  perspective  in 
Fig.  21.  Its  rear  end  a is  threaded 
to  fit  the  headstock  spindle;  the 
body  b is  bored  sufficiently  large 
and  deep  to  freely  admit  the  work,  and  eight  thumbscrews 
that  are  placed  as  shown  are  used  for  holding  the  work  and 
adjusting  it  so  that  it  will  run  true. 

86.  For  special  work  that  is  to  be  done  in  large  quanti- 
ties, special  chucks  may  be  made  to  advantage.  The 
general  form  of  such  chucks  is  about  the  same  as  those  used 
for  screw-machine  work  and  turret-lathe  work.  It  is  prob- 
able that  many  forms  of  work  made  of  iron  and  soft  steel* 
and  that  are  held  by  ordinary  chucks  at  present  will  in  the 
future  be  held  by  magnetic  chucks.  These  magnetic  chucks 


GRINDING. 


45 


§ 19 

not  only  hold  the  work  securely,  but  are  not  so  liable  to 
bend  or  spring  the  work  as  the  present  methods  of  clamping. 

87.  Face-Plate  Work. — For  the  internal  grinding  of 
work  whose  form  requires  it  to  be  held  on  a face  plate, 
the  work  is  held  by  the  same  clamping  devices  used  in 
lathe  work;  these  are  applied  in  the  same  manner  as 
in  lathe  work,  and  the  truing  is  performed  in  the  same  way. 
It  must  always  be  remembered,  however,  that  grinding  is 
a very  refined  process  of  finishing  the  work,  and  that  great 
care  should  be  taken  not  to  bend  the  work  by  clamping. 


SURFACE  GRINDING. 

88.  Grinding;  on  Planer. — The  grinding  of  plane 
surfaces  was  formerly  done,  and  is  yet  largely  done,  on  an 
ordinary  planer,  which  is  temporarily  converted  into  a sur- 
face-grinding machine  by  mounting  an  emery  wheel  on  the 
cross-rail  and  providing  an  overhead  drum  for  driving  it. 
With  a planer  in  good  condition,  very  good  work  can  be  done 
in  this  manner. 

Regular  surface-grinding  machines  are  now  made;  in 
general  appearance  and  in  their  manner  of  operation  they 
greatly  resemble  the  ordinary  metal  planer,  and,  in  fact, 
may  be  said  to  occupy  the  same  state  at  present  with  respect 
to  the  planer  that  the  first  grinding  machine  for  solids  of 
revolution  occupied  with  respect  to  the  lathe. 

89.  Present  State  of  Art. — The  art  of  surface  grind- 
ing has  not  at  present  reached  the  high  state  of  perfection 
as  has  the  grinding  of  solids  of  revolution ; and  while  it  is  a 
refined  process  of  finishing  surfaces,  it  is  not  capable  of 
competing  with  planing  in  the  removal  of  metal.  As  far  as 
hardened  work  is  concerned,  it  is  the  only  practical  method 
of  producing  plane  surfaces  in  a reasonable  time.  For  the 
most  refined  work,  the  grinding  would  be  followed  by  lap- 
ping, just  as  with  solids  of  revolution. 


46 


GRINDING. 


§19 


90.  Surface-Grinding  Machine. — Fig.  22  shows  a 
surface-grinding  machine  made  by  the  Brown  & Sharpe 
Manufacturing  Company.  The  illustration  will  show  its 
general  resemblance  to  the  planer,  from  which  it  differs  only 


in  the  curved  housings  a and  b.  The  face  of  these  housings 
is  an  arc  of  a circle  struck  from  the  center  of  the  driving 
drum  c ; from  this  it  follows  that  the  tension  of  the  wheel 
driving  belt  will  remain  constant  throughout  the  whole 
range  of  movement  of  the  crosshead  d.  The  crosshead  slide 
carries  the  wheel  head  e,  which  can  be  automatically  fed 


GRINDING. 


47 


§ 10 

across  the  machine.  The  table  /"is  arranged  to  be  traversed 
by  hand  by  means  of  the  hand  wheel  g,  but  it  may  also  be 
automatically  traversed.  The  stroke  of  the  table  is  adjust- 
able for  length  and  position  by  means  of  tappets  that  operate 
a suitable  clutch  mechanism.  Surface-grinding  machines  of 
the  type  shown  in  Fig.  22  are  at  present  adapted  only  for 
grinding  surfaces  parallel  to  the  surface  of  the  table. 

91.  Selection  of  Wheels. — The  wheels  for  surface 
grinding  should  always  be  softer  than  those  used  for  grind- 
ing solids  of  revolution  in  order  to  reduce  the  pressure  of 
the  cutting  operation  and  the  consequent  generation  of 
heat.  In  surface  grinding  only  one  side  of  the  work  is 
operated  upon,  and,  consequently,  the  work,  with  any  in- 
crease in  the  temperature,  will  rise  up  in  the  center.  Since 
surface-grinding  machines  for  fine  work  are  not  at  present 
constructed  to  use  water,  it  is  necessary  to  keep  the  gen- 
eration of  heat  down  by  a proper  selection  of  grinding  wheel, 
and  thus  prevent  too  serious  a change  in  the  shape  of  the 
work. 

92.  Holding  the  Work. — The  work  is  held  to  the 
table  of  a surface-grinding  machine  by  the  same  holding 
devices  and  in  the  same  manner  as  is  done  in  planer,  shaper, 
and  milling-machine  work.  For  many  kinds  of  work,  the 
magnetic  chuck  may  be  used  successfully. 


CUTTER  AND  REAMER  GRINDING. 


PURPOSE  OF  TOOL  GRINDING. 

93.  When  making  milling  cutters  and  reamers,  it  is 
necessary  to  grind  them  so  as  to  give  them  true  cutting 
edges.  It  is  also  necessary  to  grind  such  tools  when  they 
become  dull  to  maintain  them  in  the  best  serviceable  con- 
dition. The  condition  of  all  cutting  tools  should  be  watched 
carefully,  because  when  a tool  or  cutter  begins  to  get  dull, 
if  it  is  not  immediately  sharpened  it  soon  becomes  worse, 
and  requires  more  power  to  drive  it.  Furthermore,  the 


48 


GRINDING. 


19 


increased  friction  produces  sufficient  heat  to  seriously  affect 
the  temper  of  the  tool. 

Most  tools  when  but  slightly  dulled  may  be  ground  many 
times  without  injury  either  to  their  form  or  temper.  This 
is  especially  true  of  the  formed  cutters,  of  which  the  gear- 
cutter  is  perhaps  the  most  common  type.  These  cutters 
may  be  ground  on  the  faces  of  the  teeth,  as  long  as  the 
teeth  last,  without  changing  their  form;  and  if  kept  in  good 
condition,  a very  slight  grinding  is  sufficient  to  sharpen  the 
cutter;  but,  if  the  cutter  is  kept  at  work  when  dull,  the 
formed  surfaces  become  worn  back  from  the  cutting  edge, 
thus  necessitating  the  removal  of  ^ inch  or  more  from  the 
faces  of  the  teeth  in  order  to  sharpen  them. 


THE  MACHINE. 

94.  Cutter  and  reamer  grinding  is  usually  done 
on  specially  designed  machines,  but  it  may  be  done  on  the 
universal  grinding  machine.  Several  of  these  cutter 
grinders  have  most  of  the  movements  of  the  universal 
grinding  machine;  such  cutter  grinders  will  then  serve  for 
a large  variety  of  small  work  that  is  generally  done  in  the 
universal  grinding  machine.  The  essential  features  of  a 
cutter  grinder  are  a spindle  carrying  a small  emery  wheel 
that  may  be  revolved  at  from  2,500  to  5,000  revolutions  per 
minute,  and  suitable  holders  and  guides  for  holding  and 
guiding  the  tools  in  the  correct  position.  A small  table,  or 
rest,  is  usually  provided  in  front  of  the  wheel  on  which  flat 
or  formed  cutters  may  be  held  while  being  ground. 

95.  The  machine  shown  in  Fig.  23  is  a cutter  and  reamer 
grinder  made  by  the  Norton  Emery  Wheel  Company,  and 
arranged  only  for  the  sharpening  of  milling  cutters  and 
reamers.  This  machine  consists  of  a coluqin  a that  carries 
the  wheel  stand  b;  this  is  arranged  in  such  a manner  that 
it  can  be  swiveled.  A graduated  saddle  c is  placed  on  top 
of  the  column;  this  saddle  carries  the  slide  d in  which  the 
table  e works.  The  table  can  be  moved  toward  or  away 


GRINDING. 


49 


§ 19 


from  the  grinding  wheel  by  means  of  a feed-screw  that  is 
operated  by  the  hand  wheel  f.  The  table  can  be  swiveled 
horizontally,  the  saddle  c having  graduations  that  show  the 


angle  between  its  line  of  motion  and  the  axis  of  rotation  of 
the  spindle.  A feed-screw  that  works  in  a split  nut  and  is 
operated  by  the  hand  wheel  g is  used  for  traversing  the 
table;  when  the  split  nut  is  unlocked  from  the  feed-screw, 
the  table  can  be  traversed  rapidly  by  means  of  the  pilot 


50 


GRINDING. 


§19 


wheel  h.  The  height  of  the  emery  wheel  above  the  table 
can  be  adjusted  by  means  of  the  hand  wheel  i.  A headstock  k 
and  a footstock  / are  provided  for  grinding  work  between 
centers.  The  headstock  and  footstock  are  attached  to  an 
auxiliary  swivel  table  m,  which  is  placed  on  top  of  the  reg- 
ular table  e\  this  adapts  the  machine  for  taper  work  to  be 
done  between  centers.  An  adjustable  standard  n for  a guide 
finger  is  provided;  this  finger  prevents  rotation  of  the  cut- 
ter or  reamer  that  is  being  ground.  A small  rest  o is  in- 
tended for  the  grinding  of  formed  cutters,  which  are  laid 
on  the  rest  and  presented  to  the  grinding  wheel  by  hand. 

96.  If  a driving  pulley  is  fitted  to  the  headstock,  the 
machine  may  be  used  for  grinding  small  cylindrical  and 
taper  work  between  centers,  and  by  the  aid  of  proper 
attachments  chuck  work  and  internal  grinding  of  a light 
kind  may  be  done.  Since  the  wheel  stand  may  be  swiveled 
to  bring  the  wheel  over  the  table,  the  machine  may  be  used 
for  light  surface  grinding. 

97.  Cutter  and  reamer  grinding  machines  are  made  in 
different  ways  by  the  various  manufacturers,  but  most  of 
them  embody  the  same  features  and  differ  only  in  the  design 
of  the  details.  The  illustrations  and  examples  of  cutter  and 
reamer  grinding  that  are  given  in  the  following  articles  do 
not  refer  to  any  particular  make  of  machine,  but  have  been 
selected  entirely  for  the  sake  of  the  principle  involved  in  each 
operation.  This  fact  is  mentioned  here  in  order  that  the 
reader  may  not  think  that  the  illustrations  and  explana- 
tions given  refer  to  the  machine  shown  in  Fig.  23. 


EXAMPLES  OF  CUTTER  AND  REAMER 
GRINDING. 


GRINDING  CYLINDRICAL  CUTTERS. 

98.  Cutter  Bar. — Fig.  24  is  an  example  of  grinding  a 
cylindrical  milling  cutter  in  a machine  somewhat  different 
from  that  shown  in  Fig.  23.  In  the  illustration,  which  is  a 
top  view,  the  emery  wheel  a is  shown  mounted  on  the 


GRINDING. 


51 


§ 19 

spindle  b\  beneath  the  emery  wheel  is  a guide  finger  c. 
Clamps  d,  d hold  a cutter  rod  or  bar  e on  which  the  cutter  f 
is  mounted.  A helical  groove  is  sometimes  cut  in  the  cutter 
bar  e,  so  that  any  particles  of  emery  that  may  collect  on  the 
bar  will  be  brushed  into  the  groove  by  the  backward  and  for- 
ward movement  of  the  cutter.  Since  the  size  of  the  holes  in 
milling  cutters  varies  with  their  diameter,  it  follows  that 
some  provision  must  be  made  for  grinding  all  sizes  of  cutters 


within  the  capacity  of  the  machine.  This  is  done  either  by 
making  a suitable  bar  for  each  size  of  hole  or  by  making 
bushings  for  the  larger  sizes  of  holes,  so  that  cutters  having 
large  holes  may  be  ground  on  the  small  bar.  Some  cutters 
and  shell  reamers  have  taper  holes  in  them ; these  must  be 
provided  with  a bushing  having  a straight  hole  fitting  the 
bar,  the  outside  being  fitted  to  the  taper  hole  in  the  cutter 
or  reamer.  When  this  bushing  is  in  place  in  the  cutter,  the 
latter  may  be  ground  the  same  as  any  cutter  having  a 
straight  hole. 

99.  Form  and  Position  of  Guide  Finger. — The 

cutter  having  been  mounted  on  a suitable  bar,  the  guide 


52 


GRINDING. 


19 


finger  a is  adjusted  under  one  of  the  teeth,  as  shown  in 
Fig.  25,  so  that  the  grinding  wheel  is  in  contact  with  the 
back  of  the  land  of  the  tooth.  This  guide  finger  should  be 
somewhat  wider  than  the  face  of  the  grinding  wheel,  in 
order  that  the  cutter  may  rest  on  the  finger  before  it 


reaches  and  after  it  leaves  the  grinding  wheel.  If  the  fin- 
ger is  narrower  than  the  face  of  the  wheel,  the  latter  is 
liable  to  catch  and  score  the  cutter  while  the  latter  is  enga- 
ging or  leaving  the' wheel.  The  guide  finger  should  always 
have  its  top  filed  so  that  it  is  in  contact  throughout  its  width 
with  the  face  of  the  tooth. 

lOO.  Precautions.^ — Cylindrical  cutters,  no  matter 
whether  their  teeth  are  straight  or  helical,  are  ground  by 
moving  them  past  the  face  of  the  grinding  wheel.  The 
latter  should  always  revolve  in  such  a direction  that  it  tends 
to  press  the  tooth  that  is  being  ground  against  the  guide 
finger.  The  teeth  are  then  ground  one  by  one,  preferably 
by  light  cuts,  going  several  times  around  the  cutter  to 
sharpen  it.  In  order  that  the  cutter  may  last  well,  it  is 
essential  that  the  temper  should  not  be  drawn  from  the 
teeth,  or  as  the  shopman  expresses  it,  “the  cutting  edges 
must  not  be  burned.”  Since  cutter-grinding  machines  are 
not  arranged  to  permit  the  flooding  of  the  work  with  water, 
it  follows  that  overheating  can  only  be  prevented  by  taking 
light  cuts. 


§ 19 


GRINDING. 


53 


lOl.  Cutters  ground  by  sliding  them  along  a cylindrical 
bar  become  cylindrical  themselves  on  account  of  the  fact  that 
the  distance  between  the  axes  of  rotation  of  the  grinding 
wheel  and  the  cutter  remains  constant  at  the  point  where 
the  grinding  is  taking  place,  irrespective  of  whether  the  two 
axes  are  parallel  or  inclined  with  respect  to  each  other. 
The  grinding  wheel  retaining  its  size,  it  follows  that  all  points 
of  all  teeth  of  the  cutter  will  be  the  same  distance  from  its 
axis;  that  is,  they  will  be  on  the  surface  of  a cylinder. 


GRINDING  SHANK  CUTTERS  AND  ANGULAR  CUTTERS. 

102.  Some  cutters,  especially  those  having  shanks, 
cannot  be  ground  on  a bar  in  the  manner  just  described ; 
such  cutters  are 
mounted  in  a suit- 
able socket  and  ' 
ground  cylindrical, 
or  to  a given  angle,  by 
adjusting,  by  trial, 
the  device  in  which 
they  are  mounted. 

Angular  cutters 
cannot  be  ground  by 
sliding  them  along  a 
bar,  and  the  same 
device  used  for 
shank  cutters  may 
be  used  for  them. 

Thus,  the  cutter 
may  be  mounted  on 
a bar  held  in  a swiv- 
el head  a , Fig.  26, 
which  is  set,  by  trial  or  by  graduations,  to  the  required  angle. 
The  guide  finger  having  been  adjusted,  the  cutter  is  traversed 
past  the  face  of  the  grinding  wheel  by  moving  the  table  b to 
which  the  holding  device  is  attached. 


ojZ / 

) 

| 

fig.  2i5. 


GRINDING. 


19 


54 


REAMER  GRINDING. 

1 03.  Cyl  inclrical  and  taper  shell  reamers  may  be  ground 
in  the  same  manner  as  milling  cutters,  sliding  them  along 
a bar  if  the  reamer  is  cylindrical,  and  using  a holding  de- 
vice if  the  reamer  is  tapering.  In  most  cases  it  will  be 
necessary  to  make  a bushing  for  cylindrical  shell  reamers, 
since  they  usually  have  a tapering  hole. 

104.  Reamers  that  may  be  classified  under  the  general 
heading  of  solid  reamers  generally  have  a center -at  each 


end.  Such  reamers  are  ground  between  centers,  as  is  shown 
in  Fig.  27.  For  grinding  cylindrical  reamers,  the  centers 
are  adjusted  so  that  the  line  joining  them,  which  is  also  the 
axis  of  the  reamer,  is  parallel  to  the  line  of  motion  of  the 
centers;  for  taper  reamers,  the  axis  of  the  reamer  is  set  at 
the  required  angle  to  the  line  of  motion.  In  this  particular 
case,  the  centers  are  clamped  not  directly  to  the  table,  as  in 


GRINDING. 


55 


§19 

the  cutter  grinder  that  was  illustrated  in  Fig.  23,  but  to  a 
holding  device#,  which  in  turn  is  clamped  to  the  table  b. 
The  grinding  is  done  by  traversing  the  table  b,  resting  the 
different  teeth  in  succession  on  the  guide  finger. 


GRINDING  TEETH  OF  SIDE  MIFFING  CUTTERS. 

105.  For  grinding  the  teeth  on  the  side  of  side  milling 
cutters,  the  cutter  must  be  attached  to  the  headstock  by 
means  of  a suitable  socket 
or  arbor,  as  shown  in  Fig.  28, 
where  a is  a holding  device 
or  headstock.  It  will  rarely 
be  possible,  for  want  of 
room,  to  apply  the  guide 
finger  to  the  side  tooth 
that  is  being  ground;  in 
most  cases  the  finger  will 
have  to  be  applied  to  the 
periphery  of  the  cutter.  It 
must  not  be  forgotten  that 
the  guide  finger  must  be 
placed  in  such  a position 
that  the  pressure  of  the  cut 
will  be  against  it;  this  re- 
quires the  finger  to  be 
placed  in  an  opposite  posi- 
tion whenever  the  cutter  is 
reversed  after  grinding  one  1 1G  28- 

side.  In  Fig.  28  this  fact  is  indicated  by  showing  ihe  new 
position  of  the  finger  and  the  grinding  wheel  in  dotted  lines. 
If  the  cutting  edges  of  the  side  teeth  are  to  lie  in  a plane,  the 
holding  device  a must  be  swiveled  to  secure  this  condition. 


USE  OF  CUR  WHEEF. 

106.  For  some  kinds  of  tool  grinding  and  cutter  grind- 
ing, a cup  wheel  may  be  used  to  advantage.  An  example 
showing  how  the  cup  wheel  is  applied  is  given  in  Fig.  29, 


C.  S.  III.— 9 


56 


GRINDING. 


where  an  inserted-blade  side  milling  cutters  is  seen  mounted 
on  an  arbor  held  in  an  adjustable  holder  b.  The  holder  is 
made  adjustable  in  a vertical  direction,  in  order  that  the  axis 
of  the  cutter  may  be  inclined,  in  respect  to  the  axis  of  rota- 
tion of  the  grinding  wheel  d , until  the  desired  degree  of 
clearance  is  obtained.  If  the  guide  finger  c is  used  on  the 
side  of  the  cutter,  as  shown,  it  will  be  necessary  to  clamp 


the  cutter  while  grinding  each  tooth  as  the  work  passes  off 
from  the  guide  finger  or  tooth  rest  before  cutting  begins. 
The  tooth  rest  acts  as  a spring  pawl  when  revolving  the 
cutter.  The  loop  at  the  back  of  the  tooth  rest  is  for  the 
insertion  of  the  thumb  of  the  operator  when  it  is  desired  to 
spring  the  rest  back  to  clear  the  teeth.  The  benefit  to  be 
derived  from  the  use  of  a cup  wheel  is  the  well-supported 
cutting  edge  that  is  given  to  the  cutter.  The  teeth  on  the 
side  of  the  cutter  can  be  ground  so  that  their  cutting  edges 
lie  in  a plane,  or  they  can  be  ground  so  that  their  inside  cor- 
ners have  a slight  relief,  by  a proper  horizontal  adjustment 
of  the  holder.  If  the  holder  can  be  swiveled  sufficiently, 


fig.  29. 


§ 19 


GRINDING. 


57 


angular  cutters  may  be  ground  with  a cup  wheel.  The 
depth  of  cut  is  regulated  by  feeding  the  cutter  toward  the 
wheel,  and  the  grinding  is  done  by  traversing  the  cutter 
past  the  wheel. 


USING  UNIVERSAL  GRINDING  MACHINE. 

107.  Introduction. — When  no  cutter  grinder  is  avail- 
able, the  universal  grinding  machine  may  be  used  for  cutter 
and  reamer  grinding;  and,  in  many  cases,  it  may  also  be 
used  for  work  beyond  the  range  of  the  cutter  grinder. 

108.  Grinding  a Milling  Cutter.  — Fig.  30  shows 
how  a side  milling  cutter  may  have  the  teeth  on  its  periphery 


sharpened  in  the  universal  grinding  machine.  A guide 
finger  a is  fastened  to  a suitable  bar  b.  This  finger  should 
always  be  so  arranged  as  to  be  at  rest  with  respect  to  the 
grinding  wheel ; that  is,  its  position  with  respect  to  the  grind- 
ing wheel  should  not  change.  When  the  guide  finger  is 
attached  to  the  wheel  base,  it  occupies  a fixed  position  in 
front  of  the  wheel,  and  every  part  of  the  tooth  that  is  being 
ground  must  travel  over  it  and  pass  the  wheel  in  exactly 
the  same  relative  position.  This  insures  that  the  backing- 
off  is  at  an  angle  that  is  constant  throughout  the  length  of 
each  tooth  and  is  the  same  for  all  teeth. 

109.  Mounting  Guide  Fingers.  — Sometimes  the 
guide  finger  is  mounted  on  the  machine  table,  as  shown 


58 


GRINDING. 


19 


in  Fig.  31,  in  which  case  it  travels  with  the  work.  This  will 
answer  for  grinding  short  work,  such  as  milling  cutters  less 
than  1 inch  thick  and  having  straight  teeth.  It  is  clear 
that  with  the  guide  finger  located  on  the  table,  it  is  at  rest 


with  respect  to  the  work  throughout  the  grinding;  conse- 
quently, it  cannot  rotate  the  work,  as  is  absolutely  required 
in  the  case  of  tools  with  helical  cutting  edges,  in  order  to 
present  every  point  of  each  cutting  edge  to  the  grinding 
wheel  in  exactly  the  same  manner. 

1 lO.  A beginner  is  very  likely  to  think  that  a long  cut- 
ting tool  with  straight  cutting  edges  may  satisfactorily  be 
ground  with  the  guide  finger  fixed  with  respect  to  the  work. 
This  would  be  the  case  if  there  was  no  warping  of  the  tool 
in  hardening;  but  after  the  tool  has  been  hardened,  it  will 
be  found  that  no  matter  how  true  the  grooves  were  milled, 
and  no  matter  how  carefully  the  hardening  was  done,  they 
will  have  become  warped  enough  to  prevent  proper  sharpen- 
ing. This  can  readily  be  seen  if  the  tool  is  first  ground  to 
run  true,  grinding  it  as  if  it  were  a cylinder  or  a cone. 
Then,  adjusting  the  guide  finger  so  as  to  keep  the  backing- 
off  slightly  away  from  the  cutting  edge  and  taking  the  cut, 
it  will  be  found  that  the  land  remaining  between  the  cutting 
edge  and  the  termination  of  the  backing-off  is  not  equal  in 
width  throughout  the  length  of  the  tooth ; this  shows  that 


19 


GRINDING. 


59 


if  the  backing-off  had  been  carried  clear  to  the  cutting  edge, 
the  latter  would  not  be  true  throughout  its  length. 

111.  Location  of  Guide  Finger. — The  guide  finger 
should  always  be  so  located  that  the  grinding  wheel  will  re- 
volve toward  it,  and  should  always  be  placed  between  the 
axes  of  the  grinding  wheel  and  the  work,  and  just  as  close 
to  the  edge  that  is  being  ground  as  circumstances  will  per- 
mit. It  should  always  be  applied  to  the  face  of  the  tooth, 
and  never  to  the  back,  for  the  reason  that  any  want  of  truth 
of  the  back  will  affect  the  truth  of  the  cutting  edge.  The 
mistake  of  placing  the  guide  finger  so  that  the  grinding 
wheel  runs  away  from  it  must  be  guarded  against,  on  ac- 
count of  the  liability  of  spoiling  the  work  caused  by  the 
tendency  of  the  wheel  to  rotate  the  latter. 


DIFFERENT  FORMS  AND  METHODS  OF  BACKING-OFF. 

112.  Cutter  and  reamer  teeth  are  backed  off  in  a va- 
riety of  ways.  For  some  classes  of  work  and  in  the  absence 
of  the  proper  facilities  for  grinding,  the  tool  is  turned  to  the 
exact  size  and  fluted,  after  which  it  is  backed  off  by  filing 
the  proper  clearance  on  the  teeth.  The  cutter  or  tool  is 
then  hardened  and  is  perhaps  ground  by  hand  on  a suitable 
emery  wheel  in  order  to  produce  a good  cutting  edge  and  a 
clean  surface  by  which  to  draw  the  temper.  Work  done  in 
this  manner  will  prove  entirely  satisfactory  for  a large 
variety  of  comparatively  rough  work. 

1 1 8.  Several  methods  of  backing-off  are  used,  each  hav- 
ing its  special  advantage  or  use,  which  will  be  explained  to- 
gether with  the  manner  of  the  production  of  each  one.  The 
teeth  of  cutters  and  reamers  are  left  by  the  machining  proc- 
ess somewhat  in  the  form  shown  in  Fig.  32,  which  is  exag- 
gerated for  the  sake  of  clearness.  In  Fig.  32  (tf),  a section 
of  a tooth  is  shown  in  which  a is  the  face,  and  the  land  b is 
an  arc  of  the  circle  forming  the  circumference  of  the  cutter 
or  tool.  With  the  tooth  in  this  shape,  it  is  of  little  value 
as  a cutting  tool,  and  can  do  but  very  poor  work  until  the 


60 


GRINDING. 


§19 


land  is  given  proper  clearance.  The  most  common  form  of 
clearance  is  shown  in  Fig.  32  ( b ).  An  emery  wheel  is  set  so 
as  to  grind  the  back  c'  of  the  land  away,  and  the  work  and 
grinding  wheel  are  brought  together  until  the  edge  c is 
sharp.  Obviously,  the  land  will  be  ground  hollow,  as  shown 


by  the  dotted  line  c'  c.  In  order  to  leave  a well-supported 
cutting  edge,  the  curvature  should  be  as  small  as  possible; 
this  means  that  as  large  an  emery  wheel  as  possible  should 
be  used.  The  amount  that  the  edge  c'  is  nearer  the  axis  of 
the  tool  than  the  cutting  edge  c is  regulated  by  adjusting 
the  height  of  the  guide  finger. 

114.  A better  form  of  backing-off  is  the  straight  back- 
ing-off shown  in  Fig.  32  (c)  by  the  dotted  line  e e.  This 
form  can  be  satisfactorily  produced  only  by  a cup  wheel. 
Attempts  are  occasionally  made  to  use  an  ordinary  wheel 
cutting  on  its  periphery  for  a straight  backing-off,  setting 
the  machine  so  that  the  axis  of  the  wheel  is  at  right  angles 
to  the  axis  of  the  tool.  Such  an  attempt  will  result  in  un- 
satisfactory work  owing  to  the  wear  of  the  emery  wheel,  and 
the  method  is  not  to  be  recommended. 

115.  It  is  conceded  that  the  best  form  of  backing-off 
is  as  shown  in  Fig.  32  (d)  by  the  dotted  line  f f,  which  is 
the  arc  of  a circle.  Unfortunately  this  form  of  backing- 
off  cannot  be  produced  in  the  ordinary  cutter  grinder  or 


GRINDING. 


§19 


61 


universal  grinding  machine,  but  requires  a machine  some- 
what similar  to  that  used  for  making  formed  cutters.  The 
advantages  of  this  form  of  backing-off  are  a well-supported 
cutting  edge  combined  with  ample  clearance. 

1 16.  In  the  absence  of  a special  machine,  a fair  approx- 
imation to  the  circular  backing-off  may  be  given  to  a reamer 
as  follows:  Set  the  guide  finger  so  low  that  the  wheel  will 
only  touch  the  back  of  the  tooth,  grinding  it  from  g to  g\ 
Fig.  32  ( e ),  and  take  this  cut  over  all  the  teeth.  Then 
slightly  raise  the  guide  finger  and  move  the  work  and  wheel 
apart;  now  again  bring  the  work  toward  the  wheel  until  it 
cuts  from  h to  h' . Continue  this  cycle  of  operations  until 
the  edge  k'  is  reached.  The  top  of  the  land  will  be  a suc- 
cession of  ridges  that  may  be  smoothed  down  by  careful 
oilstoning  to  a very  good  imitation  of  the  backing-off  that  a 
special  machine  will  produce.  The  method  just  explained 
is  not  recommended  for  any  other  cutting  tools  than  reamers. 
In  practice  the  form  of  tooth  shown  in  Fig.  32  (b)  is  gen- 
erally used. 


SHARPENING  FORMED  CUTTERS. 

117.  Fig.  33  shows  the  method  of  grinding  a formed 
gear-cutter.  The  cutter  is  mounted  on  a stud  a in  such  a 
manner  that  the  axis  of  rotation  of  the  grinding  wheel  b is 
in  the  plane  midway  between  the  sides  of  the  cutter.  A 
guide  finger  c is  set  against  the  back  of  the  teeth  and  is  so 
adjusted  as  to  make  the  face  of  the  teeth  radial.  The  slide 
on  which  the  stud  is  carried  may  be  pushed  in  or  out  by  hand 
while  the  table  remains  stationary. 

When  formed  cutters  are  ground  by  hand,  a rest  is  placed 
in  front  of  the  wheel  and  the  cutter  laid  upon  this  rest.  The 
cutter  is  then  pushed  and  pulled  back  and  forth  while  the  face 
of  the  tooth  is  held  against  the  grinding  wheel.  The  rest 
is  often  dispensed  with  in  grinding  formed  cutters;  con- 
siderable care  will  then  be  required  to  grind  the  faces  of 
the  teeth  at  right  angles  to  the  sides  of  the  cutter.  Long 


62 


GRINDING. 


§ 19 

formed  cutters  may  be  mounted  on  a bar  and  moved  back 
and  forth  along  this  bar  until  the  guide  finger  is  in  contact 


with  the  back  of  the  tooth.  The  wheel  used  should  be  of 
the  dished  type;  that  is,  it  should  be  as  shown  in  Fig.  33. 


CLEARANCE. 

118.  Various  workmen  differ  greatly  as  to  the  proper 
clearance  for  different  cutting  tools,  but  the  following  is 
probably  good  average  practice.  The  teeth  of  milling  cut- 
ters should  be  so  ground  for  iron  and  steel  that  they  will 
have  about  3 degrees  clearance.  Less  clearance  is  apt  to 
make  them  drag  and  cut  slowly,  and  more  will  make  them 
chatter.  Cutters  intended  for  soft  metals  need  a greater 
clearance.  The  amount  of  clearance  that  the  teeth  of  cut- 
ters and  reamers  should  have  is  easily  determined  by  putting 
the  tool  into  a ring  of  corresponding  size  and  looking  through 


19 


GRINDING. 


63 


it  toward  the  light.  The  angle  of  clearance  of  any  cutter 
may  be  found  by  setting  one  blade  of  a universal  bevel  to 
the  face  of  the  tooth  and  the  other  to  the  clearance;  the 
bevel  may  then  be  laid  upon  a piece  of  paper  and  the  angle 
included  in  the  gauge  may  be  extended  and  measured  by 
any  form  of  protractor. 


GRINDING  CUTTERS  IN  PLACE. 

119.  Large  milling  cutters  are  often  ground  while  on 
their  own  arbors  and  in  the  milling  machine,  using  a special 
grinding  device  for  the  purpose.  This  is  done  for  two 
reasons:  in  the  first  place,  their  size  prevents  them  from 
being  ground  in  a cutter  grinder;  in  the  second  place,  grind- 
ing them  on  their  own  arbor  insures  that  they  will  run  true. 


LAPPING. 


THE  TOOLS. 


DEFINITION  AND  PURPOSE. 

120.  Lapping  is  an  abrading  process  in  which  the 
abrading  material,  as  emery,  is  embedded  in  some  soft 
metal,  as  cast  iron,  brass,  or  lead.  It  is  an  extension  of  the 
grinding  process  and  is  aptly  said  to  be  the  refinement  of 
grinding.  In  this  process,  the  results  depend  largely  on 
the  skill  of  the  operator,  and  bear  about  the  same  relation 
to  the  finishing  of  ground  work  that  scraping  bears  to  the 
final  finishing  of  planed  surfaces.  The  lapping  process  may 
be  used  for  finishing  the  surfaces  of  unhardened  metal 
where  great  accuracy  is  required ; it  is  more  frequently 
used,  however,  for  the  final  finishing  of  hardened  work. 

121.  The  tools  used  for  lapping  are  quite  simple.  For 
lapping  holes  the  simplest  lap  is  made  of  lead  that  is  cast 
around  an  iron  or  steel  arbor,  which  arbor  may  be  made  of 


G4 


GRINDING. 


§ 19 

square  material,  or  it  may  be  round  and  have  a groove  run- 
ning lengthwise,  in  order  that  the  lead  will  turn  with  the 
arbor.  A more  elaborate  form  of  lap  that  is  intended  for 
cylindrical  holes  is  made  of  cast  iron  in  the  form  of  a split 
shell  that  is  placed  on  a tapering  arbor  and  caused  to  turn 
with  it  by  means  of  a dowel-pin.  By  driving  the  shell  far- 
ther up  the  arbor,  it  is  slightly  expanded.  Brass  is  a very 
good  material  of  which  to  construct  a lap;  it  is  rather 
expensive,  however.  Machinery  steel  is  often  used,  but  it 
cannot  be  said  to  make  as  good  a lap  as  cast  iron  or  lead  on 
account  of  the  difficulty  of  embedding  the  grinding  material 
in  it. 


USING  A LAP. 

122.  Internal  Lapping.  — In  use,  a lap  is  charged 
with  emery  and  oil  and  is  then  rapidly  passed  back  and  forth 
across  the  work,  or  vice  versa.  If  the  lap  is  intended  for  a 
cylindrical  hole,  it  must  obviously  be  slightly  smaller  than 
the  hole  in  order  that  it  may  enter  when  charged  with 
emery,  but  if  a true  hole  is  desired,  the  lap  must  be  as  large 
as  can  be  worked  in  the  hole.  For  finishing  laps  on  fine 
work  no  allowance  is  made  for  the  cutting  material  when 
making  the  lap.  When  a lap  ceases  to  cut,  it  must  be  ex- 
panded or  a new  one  made.  When  the  lap  is  made  of  lead, 
it  can  often  be  expanded  by  driving  the  arbor  home  a little, 
holding  the  lap  in  one  hand.  The  lead,  being  soft,  will 
stretch  quite  easily.  It  will  be  found,  however,  that  after 
a lead  lap  has  been  expanded  two  or  three  times  in  this 
manner,  its  surface  will  be  uneven;  a new  lap  must  then  be 
made.  It  will  be  understood  that  the  work  or  the  lap 
must  rotate  at  a fairly  high  speed  during  the  lapping  proc- 
ess. While  the  lapping  can  be  done  in  a grinding  machine, 
it  is  usually  more  convenient  to  use  a hand  lathe. 

123.  Grade  of  Emery. — The  grade  of  emery  that  is 
to  be  used  depends  on  the  amount  of  stock  that  is  to  be 
removed  and  the  degree  of  finish  that  is  desired.  Thus,  for 
the  finest  finish,  like  that  given  to  cylindrical  standard 


GRINDING. 


65 


§19 

gauges,  the  very  finest  of  flour  emery  must  be  used;  if  the 
lapping  process  is  used  to  rough  down  a piece  of  work  be- 
cause no  grinding  machine  is  available,  a coarse  grade  of 
emery  may  be  used.  In  order  that  the  lap  may  work  well, 
it  is  essential  to  supply  it  with  plenty  of  oil. 

1 24-.  Lapping  a Conical  Hole. — A conical  hole  is 
rather  difficult  to  lap  smooth,  because  the  lap  cannot  be 
drawn  back  and  forth  across  the  surface.  Because  of  this 
fact,  the  lap  is  very  liable  to  cut  concentric  ridges  into  the 
work;  furthermore,  the  grinding  material  is  likely  to  creep 
toward  the  larger  end  of  the  lap,  by  reason  of  the  action  of 
the  centrifugal  force  due  to  the  rapid  rotation  of  the  lap. 
This  will  cause  the  lap  to  grind  the  hole  to  a different  taper 
than  that  given  to  the  lap;  but  this  tendency  can  be  counter- 
acted somewhat  by  cutting  into  the  lap  a spiral  groove 
having  a direction  of  rotation  opposite  to  that  of  the  lap. 
Thus,  if  the  taper  lap  shown  in  Fig.  34  (a)  turns  in  the 


direction  of  the  arrow  x,  the  groove  should  be  left-handed, 
but  if  it  turns  as  shown  by  the  arrowy  in  Fig.  34  {b)\  the 
groove  should  be  right-handed.  Several  laps  will  have  to 
be  used  to  lap  the  hole  smooth  and  especial  attention  must 
be  paid  to  the  prevention  of  glazing.  In  lapping  conical 
holes,  much  finer  emery  should  be  used  than  for  cylindrical 
lapping. 

125.  External  Lapping. — An  external  lap  is  usually 
made  in  the  form  of  a ring  that  is  lined  with  lead,  brass,  or 
cast  iron.  The  length  of  the  lap  should  be  not  less  than 
1 diameter  for  a cylinder,  and  can  profitably  be  more. 
The  ring  may  be  split  and  a screw  provided  for  closing  in 


66 


GRINDING. 


§19 


the  lap  when  it  has  become  so  worn  that  it  will  not  cut. 
When  much  external  lapping  is  to  be  done,  the  ring  may 
be  provided  with  a handle  about  15  inches  long  for  the  sake 
of  convenience  in  using  it. 

120.  Lapping  Odd  Shapes. — Odd  shapes  are  some- 
times lapped  to  bring  them  to  the  required  degree  of  truth 
and  finish.  Work  having  an  odd  shape  is  made  as  nearly 
perfect  as  possible  by  machining;  a lap  is  then  made  by 
casting  lead  on  the  part  to  be  finished.  Laps  of  this  kind 
cannot  be  moved  back  and  forth  to  prevent  their  cutting 
rings  into  the  work.  For  this  reason  the  same  precautions 
should  be  taken  that  were  mentioned  in  connection  with  laps 
for  taper  work. 

127.  Lapping  Holes  of  Milling  Cutters. — While 
the  hole  of  a solid  milling  cutter  can  best  be  finished  by 
grinding  it  in  a regular  grinding  machine,  there  are  many 
places  where,  on  account  of  the  absence  of  such  a machine, 
grinding  is  impossible.  Lapping  may  then  be  used.  A lap 
that  is  small  enough  to  enter  the  hole  is  placed  between  the 
centers  of  a hand  lathe  and,  after  coating  the  lap  with  oil 
and  emery,  the  cutter  is  placed  on  it.  It  is  not  advisable 
to  attempt  to  hold  the  cutter  with  the  bare  hand  on  account 
of  the  danger  of  an  accident;  a strip  of  pine  board  may  be 
used  to  advantage  in  rotating  the  cutter,  using  it  in  the 
same  manner  as  you  would  a file.  While  the  lap  is  rotating, 
the  cutter  should  be  moved  back  and  forth  from  one  end  of 
the  lap  to  the  other  until  the  lap  ceases  to  cut.  A new  lap 
is  then  made  or  the  old  one  expanded,  and  the  lapping  con- 
tinued until  the  hole  is  of  the  correct  size. 

128.  Lapping  Valve  Seats  of  Piston  Valves. — 

The  valve  seats  for  the  piston  valves  used  in  some  makes  of 
steam  engines  for  the  distribution  of  the  steam  must  be 
truly  cylindrical  and  very  smooth  in  order  that  the  leak- 
age of  steam  and  the  wear  may  be  reduced  to  the  lowest 
limit.  In  some  cases  these  seats  are  finished  by  first  grind- 
ing or  reaming  them  when  they  are  in  place  in  the  steam 
chest,  and  then  lapping  them  in  order  to  obtain  a very 


19 


GRINDING. 


67 


fine  and  smooth  surface.  The  lap  may  be  made  of  any 
suitable  material;  after  being  charged  with  flour  emery  it 
is  pushed  back  and  forth  through  the  valve  seats,  being 
rotated  alternately  to  the  right  and  left,  until  it  ceases  to 
cut.  A slightly  larger  lap  is  then  introduced,  and  the 
operation  of  lapping  is  repeated  until  the  seats  are  truly 
cylindrical  and  smooth.  It  is  essential  that  the  lap  itself 
should  be  as  nearly  cylindrical  as  it  can  be  made.  The  num- 
ber of  laps  that  will  be  required  for  each  pair  of  valve  seats 
depends  on  the  condition  and  alinement  of  the  two  seats. 


129.  Lapping  Plane  Surfaces.  — The  lap  may  be 

made  of  any  suitable  material,  though  cast  iron  is  thought  to 
be  the  most  satisfactory.  The  face  of  the  lap  is  planed  as 
true  as  possible  and  covered  with  oil  and  emery,  after  which 
the  work  is  rubbed  over  it,  changing  the  work  around 
frequently  and  rubbing  it  in  all  directions.  Great  care  is 
required  to  prevent  crowning  the  work,  that  is,  lapping  the 
edges  away  faster  than  the  center.  The  lap  must  be  planed 
off  frequently,  as  it  wears  out  of  true  quite  rapidly. 


130.  When  the  work  is  of  such  a nature  that  it  is  easily 
tipped  by  being  moved  about,  it  should  be  placed  in  a 
holder  of  some  kind  that 
will  prevent  this.  Thus, 
suppose  that  the  rect- 
angular bar  shown  in 
Fig.  35  (a)  is  to  be  lapped 
on  the  ends  so  that  they 
are  at  right  angles  to  the 
surfaces  a and  b , and, 
consequently,  parallel.  A 
block  may  then  be  made 
with  a V groove  planed 
in  one  surface  at  right 
angles  to  the  bottom  surface,  as  shown  in  Fig.  35  (b). 
The  work  is  placed  into  this  groove,  and,  if  small,  may  be 
held  there  by  having  a few  rubber  bands  placed  over  it. 
The  holder  and  the  work  are  then  rubbed  over  the  lap.  It 


Fig.  35. 


68 


GRINDING. 


§19 


is  seen  that  the  holder  insures  the  lapping  of  the  ends  of  the 
work  at  the  proper  angle,  and  at  the  same  time  prevents 
the  work  from  being  tipped. 

131.  Lapping  Circular  Arcs. — It  is  sometimes  nec- 
essary to  lap  an  arc  of  a circle  to  an  exact  radius.  This  can 
be  done  by  a cylindrical  lap  having  a corresponding  diam- 
eter. The  lap  may  be  held  between  the  centers  of  a lathe, 
where  it  is  driven  by  a dog.  An  angle  plate  may  then  be 
clamped  to  the  slide  rest,  and  the  work  may  either  be  held 
by  hand  or  be  clamped  against  the  angle  plate.  While  the 
work  is  pressed  against  the  revolving  lap,  the  slide  rest  is 
moved  rapidly  back  and  forth.  The  action  of  the  lap  in 
this  case  may  be  likened  to  that  of  an  emery  wheel  grind- 
ing a concave  surface  into  the  end  of  a piece  that  is  held 
stationary  on  the  rest  of  a grinding  machine. 

132.  Lapping  Diamond  Tools. — While  the  use  of 

diamonds  for  taking  light  finishing  cuts  on  metals,  both  in 
turning  and  boring,  is  not  general,  there  are  still  quite  a 
number  of  shops  in  which  diamond  tools  are  used  for  finish- 
ing duplicate  work.  The  diamond  is  used  chiefly  because 
its  hardness  prevents  a rapid  wear;  then,  as  the  expense  of 
sharpening  tools  is  thus  greatly  reduced,  it  will  be  found 
that  on  many  classes  of  light  work  the  diamond  tool,  in 
spite  of  its  great  first  cost;,  will  prove  much  more  economical 
than  steel  tools.  Diamond  tools  are  not  adapted  for  heavy 
cuts,  being  too  brittle  to  stand  much  pressure;  they  answer 
admirably,  however,  for  very  light  finishing  cuts,  and  as  they 
hold  their  edge  well  and  permit  a much  greater  cutting  speed 
to  be  used  than  will  a steel  tool,  they  tend  to  increase  the 
output  of  the  machine. 

133.  For  this  work  the  black  diamond  and  the  bort 

are  the  kinds  usually  used,  though  sometimes  white  dia- 
monds are  used.  The  stone  is  set  into  a hole  drilled  in  an 
iron  or  steel  holder,  and  is  lightly  held  by  peening  the 
metal  toward  the  stone.  The  holder,  with  the  diamond  on 
top,  is  then  sometimes  put  into  a fire  and  the  stone  is 
securely  brazed  in,  leaving  but  a small  part  projecting  from 


GRINDING. 


69 


§ 19 

the  holder.  In  other  cases  the  diamond  is  fastened  without 
brazing,  the  metal  being  carefully  peened  about  the  stone. 
After  the  surplus  metal  has  been  filed  away,  a proper  cut- 
ting edge  is  ground  on  the  diamond.  For  this  purpose 
a cast-iron  or  machinery-steel  wheel  about  inch  wide 
and  6 inches  diameter,  running  about  1,000  revolutions  per 
minute,  is  used.  The  periphery  of  this  wheel  is  charged 
with  diamond  dust,  which  is  either  rolled  in  with  a small 
roller  or  hammered  in  with  a small  hammer.  The  grind- 
ing, or  lapping,  as  many  call  it,  is  then  done  by  using  the 
wheel  in  the  same  manner  as  an  emery  wheel  is  used,  the 
diamond  being  lightly  held  against  the  wheel.  Owing  to 
the  hardness  of  the  diamond,  the  process  of  lapping  it  to  the 
required  shape  is  naturally  a slow  one. 


BENCH,  VISE,  AND  FLOOR  WORK, 

(PART  1.) 


INTRODUCTION. 

1.  The  machine-shop  operations  previously  considered 
have  been  almost  entirely  associated  with  'machine  tools. 
Aside  from  these,  there  is  a large  amount  of  work  done  by 
hand,  such  as  laying  out,  chipping,  filing,  scraping,  fitting, 
etc.  These  operations  are  usually  performed  either  on  a 
bench  or  on  the  floor,  depending  on  the  size  or  weight  of 
the  work;  hence,  the  name  bench , vise , and  floor  work. 

Bench  work  is  of  a lighter  nature  than  floor  work,  though 
it  may,  and  often  does,  include  the  entire  finishing  and 
erecting  process  where  the  machine  is  small,  and  in  the  case 
of  large  work  many  of  the  small  parts  are  assembled  at  the 
bench  and  are  then  taken  to  the  floor  and  adjusted  to  the 
other  parts. 

Floor  work  includes  the  erecting  and  assembling  of  heavy 
machines  and  the  machining  of  parts  too  heavy  or  too  large 
to  be  operated  on  in  the  stationary  machine  tools.  In  the 
latter  case  the  heavy  parts  are  set  up  at  a convenient  place 
on  the  floor  and  the  machining  done  by  means  of  portable 
tools  set  up  at  a suitable  location  for  each  operation.  Under 
this  heading  the  tools  and  processes  employed  will  be  con- 
sidered, as  well  as  the  work  itself. 

§20 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 

C.  S.  AIL— 10 


2 


BENCH,  VISE,  AND  FJ.OOR  WORK.  § 20 


BENCH  ANI)  VISE  WORK. 


FOODS  AND  FIXTURES  EMPLOYED. 


TOOLS. 

Hammers. — Machine-shop  practice  calls  for  a vari- 
ety of  operations  that  may  be  classed  as  hammering.  A 

blow  struck  may  be 
only  the  fraction  of  an 
ounce,  such  as  a tool- 
maker  strikes  on  his 
prick  punch  in  laying 
out  accurate  centers, 
or  it  may  be  a blow 
delivered  by  a ram 
weighing  a half  ton 
and  pushed  by  a dozen 
men.  The  hammers 
used  by  machinists 
weigh  from  ^ to  2 pounds,  and  are  designated  as  ball-peen, 
straight-peen,  and  cross-peen.  The  one  most  com- 
monly used  is  the  ball-peen  hammer,  weighing  from  1 to 
lj  pounds;  it  is  shown  in  Fig.  1 (a).  This  hammer  is  used 
for  all  ordinary  work,  including  riveting,  and  the  effect  of 
the  blow  struck  by  the  ball  is  equal  in  all  directions.  The 
straight-peen,  Fig.  1 ( b ),  and  cross-peen,  Fig.  1 (^),  are 
used  when  the  effect  of  the  blow  must  be  greater  one  way 
than  the  other.  The  smallest  sizes  of  hammers  are  used  on 
light  work,  such  as  prick  marking  and  finishing  on  dies. 

3.  Center  and  Prick  Punches. — Center  punches, 
which  are  illustrated  in  Fig.  2 (a),  are  used,  as  their  names 
indicate,  for  punching  the  centers  of  holes  to  be  drilled  in 
the  ends  of  shafts  and  similar  pieces  that  are  to  be  turned 
in  the  lathe,  and  also  for  making  a mark  or  hole  for  start- 
ing a drill  in  any  drilling  work, 


§ 20  BENCH,  VISE  AND  FLOOR  WORK.  3 

The  prick  punch  shown  in  Fig.  2 (b)  is  similar  to  the 
center  punch,  but  may  be  smaller,  and  must  have  a sharp, 
well-ground  point.  The  prick  punch  is  only  used  to  make 


Fig.  2. 


the  light  marks  in  laying  out  work,  while  the  center  punch 
is  used  to  make  a larger  hole  and  often  to  move  a center 
hole  one  way  or  another.  Center  punches  should  be  ground 
to  an  angle  of  60°. 

4.  The  Marker. — The  marker  shown  in  Fig.  2 ( c ) is  a 
center  punch  made  of  octagon  steel ; the  part  a is  turned  to 
the  size  of  the  holes  to  be  marked  off,  and  the  center  b pro- 
jects about  inch.  In  boiler  work,  rows  of  holes  are  first 
punched  in  the  edges  of  the  plates,  which  are  then  bolted  in 
place ; the  circular  part  a of  the  marker  is  put  through  the 
holes  in  the  first  sheet  and  a blow  struck  on  the  head  drives 
the  point  b into  the  under  sheet,  thus  making  a mark  for  the 
center  of  the  punch.  When  all  the  holes  are  marked  off,  the 
sheet  goes  to  the  machine  and  the  holes  are  made  as  marked. 
The  size  c of  the  marking  punch  must  in  all  cases  be  the 
same  as  that  of  the  punched  hole.  The  marker  is  a tool  that 
is  also  used  in  the  machine  shop  to  some  extent. 


4 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


Holes  that  are  laid  out  for  drilling  have  a cirele  drawn  to 
their  diameter  with  a pair  of  dividers.  Where  large  num- 
bers of  these  are  to  be  drawn,  a tool  like  that  shown  in 
Fig.  2 (d)  is  useful.  This  may  be  made  from  a piece  of 
round  steel  turned  as  shown  at  a,  making  a center  punch 
surrounded  by  a sharp  ring  b.  The  point  of  this  tool  is 
placed  in  the  prick-punch  mark  that  shows  the  center  of  the 
hole,  and  a blow  on  the  head  of  the  tool  locates  the  circle. 
In  some  cases,  the  diameter  b of  the  tool  is  made  the  same  as 
the  diameter  of  the  hole  to  be  drilled,  though  for  some  work 
it  is  made  larger  than  the  hole  and  shows  whether  the  work 
has  been  properly  drilled. 

The  cup  center,  Fig.  ,2  ( e ),  may  be  conveniently  used  on 
work  having  true  ends. 

5.  The  Scriher. — The  scriber,  which  is  usually  made 
in  the  form  shown  in  Fig.  3 ( a ),  is  commonly  made  of  a piece 

" » 333^7" - nr 

(a) 

f==~'  ' ' 


i . ^ nAYA  - - - * 

, T ir~W 

(b) 


Fig.  3. 


of  ^--inch  steel  wire,  from  6 to  10' inches  long,  ground  sharp 
on  both  ends,  twisted  in  the  middle  so  as  to  be  easily  held  in 
the  hand,  and  with  one  end  bent  at  right  angles  to  the  main 
part.  It  is  hardened  and  tempered  so  that  it  will  scratch 


20 


BENCH,  VISE,  AND  FLOOR  WORK. 


5 


any  metal  but  hardened  steel,  and  it  is  used  for  drawing 
lines  in  laying  out  work;  it  may  be  called  the  machinist's 
pencil.  Improved  scribers,  Fig.  3 ( b ) and  ( c ),  with  nurled 
handles  and  inserted  scribing  points  of  fine  quality,  are 
made  by  tool  manufacturers,  and  may  be  bought  at  reason- 
able prices.  The  first  of  these  has  a solid  handle  into  which 
the  points  are  screwed ; the  second  has  a hollow  handle 
with  a screw  chuck  at  each  end,  which  is  slipped  over 
single-  or  double-pointed  markers  and  clamped  wherever 
desired. 

6.  Bencli  Centers. — The  bench  centers  illustrated  in 
Fig.  4 are  for  the  convenience  of  the  viseman  in  centering 
work  for  the  lathe.  The 
centers  a and  b may  be 
set  at  any  location  along 
the  rod  c.  The  head  d 
is  provided  with  either 
a spring  or  a screw  cen- 
ter, so  that  the  piece 
can  easily  be  put  in 
place  or  removed. 

The  operator  takes  the  piece  to  be  centered,  puts  it  in  the 
vise,  and  center-punches  it  as  nearly  as  possible  in  the 
center.  He  now  puts  it  in  the  bench  center  and  rotates  it, 
noting  whether  it  runs  out,  and  how  much.  Having  found 
which  side  is  out  of  the  center  by  marking  with  chalk,  he 
proceeds  to  draw  the  center  hole  over  toward  that  side  with 
the  center  punch.  This  operation  must  be  repeated  until 
the  piece  runs  true  enough  to  finish.  If  the  middle  of  the 
piece  is  out  of  true  or  is  crooked,  it  should  be  straightened 
by  hammering  or  by  bending  in  the  screw-straightening 
press  e,  back  of  the  centers.  The  straightening  press  con- 
sists of  two  movable  V blocks  f,f  resting  on  a base  g,  and  a 
screw  h with  a V point  on  the  lower  end,  the  screw  being  sup- 
ported in  a frame,  as  shown.  To  straighten  a piece,  it  is  laid 
upon  the  blocks  ft  ft  with  the  bend  up,  and  the  screw 
lowered  until  the  bend  is  removed. 


6 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


7.  Hand  Hack  Saws. — The  hack  saw  is  a tool  of  grow- 
ing importance  in  the  machine  shop,  as  well  as  in  many  other 
places.  These  tools  were  formerly  rarely  met  with,  as  they 
were  high  in  price  and  much  labor  was  required  to  keep 
them  filed  sharp  enough  to  be  of  any  great  service.  Hack- 
saw blades  are  now  made  in  lengths  of  from  6 to  16  inches 
and  even  longer,  and  may  be  used  either  in  hand  frames  or 
in  specially  designed  power  machines. 

The  hand  frame  illustrated  in  Fig.  5 (a)  is  an  adjustable 
frame  in  which  blades  from  8 to  12  inches  long  can  be  used. 

The  clamps  holding  the 
blade  may  be  set  in  four 
positions,  which  allow 
the  saw  to  be  operated 
in  any  direction. 
Fig.  5 ( b ) shows  the 
blade  set  at  right  angles 
to  the  plane  of  the 
frame  to  cut  length- 
wise of  the  piece. 

8.  Power  Hack  Saw. — The  power  hack  saw  illustrated 
in  Fig.  6 in  many  instances  takes  the  place  of  the  cutting-off 
lathe.  These  machines  are  provided  with  a vise  for  holding 
the  stock  to  be  cut  off,  and  are  made  to  stop  when  the  piece 
is  cut  through.  The  blades  used  in  the  machine  are  gen- 
erally 12  or  more  inches  long;  they  will  cut  stock  as  large 
as  4 inches  in  diameter,  and  will  cut  any  metal  not  hardened 
or  tempered.  The  power  saw  has  a great  advantage  over 
the  cutting-off  machine,  in  that  it  will  cut  stock  of  any 
irregular  section.  It  is  especially  adapted  to  cutting 
off  tool  steel,  which  it  does  quickly,  with  very  slight 
waste.  The  saw  frame  of  this  machine  has  an  upward 
motion  during  the  back  stroke  that  lifts  the  teeth  off 
the  piece  being  sawed,  thus  saving  the  points  of  the 
teeth. 

Hack-saw  blades  are  so  hard  that  they  cannot  be  filed,  and 
so  cheap  that  when  dull  they  may  be  thrown  away.  They 


(a) 


*11=0 


(b) 


Fig.  5. 


BENCH,  VISE,  AND  FLOOR  WORK. 


7 


20 


are  made  with  about  25  teeth  per  inch  for  sawing  thin  metal, 
brass  tubing,  and  pipe,  and  with  about  14  teeth  per  inch 
for  other  work.  The  blades  used  in  hand  frames  are  about 
yff-g-  inch  thick  and  ^ inch  wide,  an  8-  or  10-inch  blade  being 
the  most  economical.  Longer  blades  can  be  used  in  the 
power-driven  hack  saw  than  in  the  hand  hack  saw,  on  account 
of  the  fact  that  in  the  power  machine  the  blade  is  guided 
uniformly  in  a straight  line,  while  in  the  hand  hack  saw  the 


blade  is  liable  to  run  unevenly,  and  so  to  become  cramped 
and  broken.  The  blade  best  suited  to  the  machine  has  about 
12  teeth  to  the  inch,  is  about  Tf « inch  thick,  and  | inch  wide. 

Hack-saw  blades,  while  very  hard,  have  a fair  amount  of 
elasticity;  10-inch  blades  of  the  best  makes  may  be  bent  to 
a half  circle  without  breaking.  In  hand  work,  the  operator 
should  lift  the  frame  up  slightly  when  drawing  the  saw 
back,  as  the  back  stroke  is  more  destructive  to  the  teeth 
than  the  forward  stroke. 


8 


BENCH,  VISE,  AND  FLOOR  WORK.  §20 


CLAMPING  ANI)  HOLDING  DEVICES. 

9.  Introduction.  — In  the  machine  shop  a large 
amount  of  work  is  necessarily  done  by  hand,  and  holding 
and  clamping  devices  of  various  sorts  are  required  for  pieces 
that  are  not  heavy  enough  so  that  their  own  weight  will  give 
them  the  necessary  stability.  The  parallel  jaw  vise  will 
hold  nearly  all  plane  pieces,  and  special  jaws  or  devices  are 
made  for  holding  irregular  and  special  forms.  Several 
types  of  vises  and  special  devices  will  be  illustrated  and 

described,  and  these  may 
serve  to  suggest  others 
suitable  for  special  oper- 
ations. 


1().  Screw  Vise.— 

In  Fig.  7 is  illustrated  a 
heavy  form  of  ironwork- 
er’s vise  designed  for  the 
largest,  heaviest,  and 
roughest  class  of  work. 
The  jaws  are  made  as 
large  as  8 inches  wide  ; 
and  while  this  type  is 
useful  for  large  work,  it 
is  also  copied  in  the  well- 
known  hand  vise  with 
jaws  1 inch  or  less  in 
width.  In  this  vise  the 
jaw  is  operated  by  the 
screw,  which  requires 
considerable  time  for  its  manipulation.  Where  a vise 
has  to  be  operated  frequently  or  through  a considerable 
portion  of  its  jaw  traverse,  some  special  provision  must 
be  made. 

11.  Rapid-Motion  Vise.— In  Fig.  8 is  an  illustration 
of  a vise  so  constructed  that  the  operator  simply  pushes  the 


BENCH,  VISE,  AND  FLOOR  WORK. 


9 


g 20 


cam-handle  a away  from  him  with  his  right  hand,  and  thus 
releases  the  work  and  allows  the  movable  jaw  b to  be 
rapidly  pushed  or  pulled  into 
any  position.  The  work  is 
placed  between  the  jaws  and 
gripped  by  a pull  on  the  lever. 


1 2.  Swivel  Vise. — For 

the  tool  room  and  many 
places  where  light  or  fine 
work  is  done,  a screw  vise 

like  that  shown  in  Fig.  9 is  frequently  used.  This  vise  is 
made  in  various  sizes  up  to  those  with  7-inch  jaws.  A com- 
mon size  for  tool-room  use  has  a jaw  2-f  inches  wide.  The 

back  jaw  a is  hinged  and 
held  parallel  with  the  front 
jaw  by  a taper  pin  b,  as 
shown.  It  is  often  desired 
to  hold  wedge-shaped  pieces, 
and  for  this  work  the  pin  b 
is  removed  and  the  pres- 
sure of  the  fixed  jaw  against 
the  work  rotates  the  mov- 
able jaw  to  conform  to  the 
piece  held.  This  vise  is 
also  provided  with  a base  plate  c , which  is  bolted  fast  to 
the  bench.  The  vise  proper  is  swiveled  to  this  base  and 
held  in  any  desired  position  by  the  pin  d , which  is 
drawn  up  to  release  the  vise  and  dropped  into  one  of  a 
series  of  holes  in  the  base  when  the  vise  is  in  the  proper 
position. 


13.  Pipe  Vise. — The  pipe  vise  is  a special  form  of  tool 
made  for  firmly  gripping  pipe  or  other  hollow  pieces  that 
would  be  crushed  if  gripped  in  the  ordinary  vise.  Fig.  10 
illustrates  one  of  the  best  forms  of  vise  for  this  class  of 
work.  The  pipe  is  gripped  between  two  jaws  a'  held  in  a 
malleable-iron  frame  with  a movable  top  d hinged  at  e. 


10 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


When  in  use,  the  free  side  of  the  top  d is  held  in  place  by 
the  pin  f.  The  hinged  top  on  this  vise  allows  fittings  to  be 
screwed  to  both  ends  of  a piece  of  pipe,  and  then,  by  simply 
withdrawing  the  pin  f,  the  whole  top  of  the  vise  may  be 

thrown  back  clear  of 
the  work,  which  can 
be  lifted  out  instead 
of  being  pulled 
through  the  jaws. 


14.  Vise  Jaws. 

All  the  vises  illus- 
trated are  made  of 
cast  iron,  except  the 
pipe  vise,  which  is 
of  malleable  iron. 
These  materials 
make  poor  gripping 
surfaces,  so  the  jaws 
are  covered  with 
welded  or  riveted 
steel  faces  having 
cross-cuts  on  them, 
in  order  to  grip 
It  is  plain  that  a piece  of  finished 


Fig.  10. 


the  work  more  firmly, 
work  gripped  in  such  a manner  would  be  seriously  marred. 
This  trouble  may  be  over- 
come by  using  the  device 
shown  in  Fig.  11,  which  is 
admirably  suited  for  holding 
the  best  finished  work.  It 
consists  of  two  pieces  a,  a 
having  shoulders  b to  keep 
them  from  falling  out  of  the 
vise.  These  pieces  are  held 
apart  by  springs  c that  press 
them  against  the  jaws  when 

the  vise  is  open,  and  they  are  faced  with  vulcanized  paper, 


11 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 

which  is  used  like  any  of  the  copper,  lead,  or  leather  pieces 
so  commonly  used  for  such  work.  An  appliance  of  this  sort 
provided  with  round  holes  of  various  sizes,  half  of  the  hole 
being  in  each  jaw,  permits  finely  polished  brass  or  nickeled 
pipe  and  similar  work  to  be  held  without  marring  the 
finish. 

15.  Special  Forms  of  Vises. — Special  forms  of 
vises  are  often  made  for  holding  work  of  such  form 
as  is  inconvenient  to  hold  in  the 
common  vise.  A good  example  of 
this  class  of  tool  is  the  filing 
stand  shown  in  Fig.  12  (a),  which 
is  a fixture  for  holding  the  swivel 
slide  of  a planer  head  while  the 
edges  are  being  finished.  This  vise, 
or  holder,  consists  of  a three-legged 
base  a,  screwed  to  the  floor,  sup- 
porting an  upright  c that  may  be 
clamped  in  any  position  by  the  set- 
screw b.  The  top  of  the  upright  is 
bent  at  right  angles  to  c and 
threaded  for  the  nut  d,  which 
clamps  the  work  e against  the  solid 
collar  /,  as  shown  in  the  detail 
view  of  Fig.  12  (b). 

16.  The  reaming  stand. 

Fig.  13,  is  another  form  of  special 
vise,  consisting  of  an  upright  a,  the  top  b of  which  carries 
four  jaws  c operated  by  the  handle  d.  This  stand  is  bolted 
to  the  floor  and  has  an  opening  e in  the  column,  so  that 
tools  may  be  run  clear  through  the  work  and  removed  at 
the  bottom.  Pulleys,  gears,  and  similar  pieces  may  be 
held  for  hand  reaming,  and  work  may  also  be  held  for 
tapping.  A similar  and,  for  some  purposes,  more  con- 
venient form  of  reaming  stand  is  made  by  fastening  a 
four-jaw  combination  or  universal  chuck  on  an  upright. 


12 


BENCH,  VTSE,  AND  FLOOR  WORK. 


20 


The  universal  chuck  has  the  advantage  in  that  for  many 

small  pieces  only  one 
screw  has  to  be 
moved  to  put  in  or 
remove  the  work. 


BENCHES. 

17.  Introduc- 
tion.—It  has  already 
been  said  that  bench 
work  is  to  be  dis- 
tinguished from  floor 
work  only  by  the  size 
and  weight  of  the 
parts  on  which  the 
work  is  to  be  done, 
the  heavier  parts 
being  placed  on  the 
floor  and  the  lighter 
on  benches  of  suit- 
able height.  The 
benches  form  a very 
important  part  of  the  equipment  of  a shop,  especially  where 
a large  amount  of  light  work  is  done.  They  are  usually 
made  about  30  to  36  inches  high,  depending  on  the  char- 
acter of  the  work,  the  lighter  work  being  done  on  the 
higher  benches.' 

The  design  of  benches  varies  greatly,  some  being  made 
stationary  and  others  portable.  The  design  must,  however, 
always  have  provision  for  attaching  a vise,  without  which 
a machinist’s  work  bench  is  not  complete.  For  this  reason 
they  are  frequently  called  vise  benches.  A number  of 
representative  benches  of  the  best  classes  in  use  are  here 
described. 

18.  General  Arrangement. — The  vise  bench  should 
be  located  along  the  side  of  the  room  where  the  best  light  is 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


13 


to  be  had.  The  north  side  of  the  building  makes  the  best 
location  for  the  bench,  because  the  light  is  more  even  at  all 
hours  of  the  day.  The  main  features  of  the  bench  must,  of 
course,  be  governed  by  the  work  to  be  done,  but  it  should 
always  be  convenient,  clean,  and  rigid.  In  many  shops  the 
bench  is  made  with  wooden  uprights  fastened  to  both  the 
wall  and  the  floor,  and  a hardwood  top,  which  is  2 inches  thick 
for  a bench  for  light  work,  and  from  3 to  4 inches  thick  for 
a bench  for  heavy  work.  The  front  of  the  bench  gets  the 
hardest  usage,  and  the  back  half  of  the  top  may  be  made 
much  thinner.  Vises  suitable  for  the  work  to  be  done 
should  be  located  at  convenient  distances  apart,  and  for 
each  vise  there  should  be  one  or  more  drawers,  each  pro- 
vided with  a lock  and  arranged  to  hold  conveniently  such 
tools  as  the  workman  may  require.  Sometimes  a tier  of 
drawers  is  put  in  instead  of  the  single  one,  while  at 
other  times  cupboards  are  preferred.  Cupboards,  how- 
ever, take  up  a great  deal  of  room  and  hold  comparatively 
little,  and  for  this  reason  the  drawers  are  usually  more 
desirable. 

1 9.  Bench  With  Cast-Iron  Legs  and  Frame. — The 

best  form  of  bench  for  general  use  is  that  illustrated  in 
Fig.  14.  A cast  support  a is  bolted  to  the  floor  and  also  to 
the  wall.  The  lower  part  has  a bracket  for  carrying  a shelf  b 
that  extends  the  whole  length  of  the  bench,  while  provision 
is  made  under  the  top  for  alternate  drawers  and  shelves. 
Provision  is  also  made  in  each  support  by  which  the  bolt 
holding  the  vise  passes  through  the  casting  and  thus  holds 
the  vise  in  the  most  rigid  position.  The  shelf  near  the  bot- 
tom is  so  placed  as  to  allow  ample  room  for  the  sweeper  to 
get  his  broom  clear  to  the  wall.  The  top  of  the  bench 
should  be  made  smooth,  and  all  the  visible  woodwork 
should  be  varnished  with  good  shellac.  This  makes  it  much 
easier  to  keep  neat  and  clean.  If  the  shop  is  heated  by 
steam,  the  pipes  may  be  placed  under  the  bench  and  open- 
ings c provided  before  the  windows.  This  insures  a rising 
current  of  warm  air  past  the  window  and  so  protects  the 


14 


BENCH,  VISE,  AND  FLOOR  WORK. 


20 


workman  from  cold  drafts.  In  the  form  shown,  a gas  pipe  d 
extends  along  the  back  of  the  bench. 


Fig.  14. 


20.  Portable  Benches. — Another  form  of  bench  is 
the  portable  bench,  of  which  Figs.  15  and  16  are  good  types. 
The  larger  of  these,  Fig.  15,  is  made  with  an  angle-iron 
frame  a carrying  a wooden  shelf  b and  having  a cast-iron 
top  d that  may  be  planed  true  and  used  as  a laying-out 
table.  It  is  provided  with  two  vises  and  drawers  e , e,  for  tools. 
This  bench  may  be  moved  to  the  work,  instead  of  taking 
the  work  to  the  bench,  which  makes  it  especially  useful  in 
large  shops  where  heavy  machinery  is  erected;  and  when 
engines  or  other  machines  are  shipped,  the  bench  is  often 
loaded  on  the  cars  as  one  of  the  erecting  tools,  and  is 
returned  to  the  shop  when  the  work  is  finished. 

The  bench  illustrated  in  Fig.  16  consists  of  a cast-iron 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK.  15 
column  a carrying  a cast-iron  top  b provided  with  two  vises, 


but  the  bench  may  be  used  without  the  vises  for  a small 
laying-out  table.  A cast  drawer  c held  by  gibs  d provides 


£ convenient  place  for  the  fools  used  by  the  workman.  This 


16  BENCH,  VISE,  AND  FLOOR  WORK.  § 20 

bench  is  easily  moved  to  any  part  of  the  shop  where  the 
work  is  being  done,  and  it  takes  up  but  little  space. 

21.  Post  Bench. — 

Fig.  17  shows  a conve- 
nient form  of  bench  that 
may  easily  be  constructed 
out  of  two  pieces  of  timber 
cut  to  fit  a post  or  column 
and  fastened  in  position 
with  two  bolts.  It  is  use- 
ful principally  as  a vise 
bench,  as  shown,  but  may 
be  used  for  a variety  of 
purposes. 


COLD  CHISELS. 

22.  Flat  Chisel.— 

The  forms  of  chisels  most 
commonly  used  are  the 
flat , cape , diamond,  groov- 
ing, and  side  chisels,  and 
the  gouge.  They  are  gen- 
erally made  from  octagon 
steel  of  such  size  as  to  be  most  convenient  for  the  work  for 
which  they  are  to  be  used.  Special  grades  of  steel  are  made 
for  chisels,  and  much  trouble  will  be  saved  by  using  these 
grades  for  this  class  of  work. 

The  flat  chisel  is  the  one  most  generally  used;  it  is 
made  in  the  form  shown  in  Fig.  18  {a)  and  ( b ).  The  width 
of  the  cutting  edge  should,  if  possible,  be  proportioned  to 
the  hardness  of  the  metal  on  which  it  is  to  be  used ; but  if 
one  width  of  chisel  must  answer  for  brass,  cast  iron,  steel, 
and  Babbitt,  lighter  blows  should  be  struck  while  cutting 
the  softer  metals,  or  the  metal  will  be  broken  away  before 
the  chisel  and  not  be  cut  smoothly.  A chisel  about  1 inch 
in- width  is  ordinarily  used  for  general  purposes. 


FIG.  17. 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


17 


For  finishing  surfaces,  the  edge  of  the  flat  chisel  should  be 
ground  square,  as  shown  in  Fig.  18  (a),  the  best  angle  for 
ordinary  work  being  about  60°,  as  shown  in  Fig.  18  ( b ). 
This  angle  may,  however,  vary  between  about  50°  and  75°, 
depending  on  the  hardness  of  the  material  to  be  chipped. 


/ \ 


(a) 


Fig.  18. 


Chisels  ground  with  square  corners,  as  shown  in  Fig.  18  (tf), 
are  apt  to  have  the  corners  broken  when  used  for  heavy 
work,  but  this  can  be  prevented  to  some  extent  by  grinding 
the  chisel  slightly  rounding,  as  shown  in  Fig.  18  (r).  This 
mode  of  grinding  is  especially  useful  for  chisels  that  are  to 


C.  S.  111.— u 


18 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


be  used  for  removing  small  amounts  of  material  from  fine 
work,  as  the  corners  are  always  in  sight  and  serve  as  guides 
to  the  operator. 

23.  Cape  Chisel. — The  cape  chisel,  which  is  shown  in 
Fig.  18  (d)  and  ( e ),  is  tfsed  for  narrow  grooves,  and  is  made 
in  widths  to  correspond  to  the  widths  of  the  grooves  to  be 
cut;  for  general  work  it  may  be  from  f to  \ inch  wide.  This 
chisel  should  be  made  wider  at  the  cutting  edge  than  it  is 
farther  back,  in  order  to  provide  side  clearance.  The  chisel 
will  then  work  easier  and  will  not  break  out  the  edges  of  the 
groove.  Where  a large  surface  is  to  be  finished  by  chipping, 
it  is  customary  to  drive  a number  of  grooves  across  it  with 
the  cape  chisel  and  then  use  a flat  chisel  to  remove  the 
stock  left  between  the  grooves. 

24.  Gouge. — The  half-round  gouge  shown  In  Fig.  18  (f) ' 
and  (g)  is  for  work  on  rounded  surfaces  or  fillets,  or  for  cut- 
ting half-round  grooves. 

25.  Diamond  Point. — The  diamond  point  shown  in 
Fig.  18  (/z)  and  (z)  is  used  for  V-shaped  grooves  or  for 
finishing  out  corners.  It  is  largely  used  with  a very  light 
hammer  in  lettering  bottle  molds,  for  which  use  it  is  made 
of  -f-inch  steel. 

26.  Grooving  Chisel. — The  grooving  chisel,  Fig.  18  (j) 
and  (b),  is  used  for  oil  grooves  and  similar  work,  and  is 
often  made  of  extra  length  to  reach  through  long  hubs. 
This  chisel  should  be  made  wider  at  its  cutting  edge  than  it 
is  farther  back,  as  in  the  case  of  the  cape  chisel;  otherwise 
it  is  apt  to  leave  a burr  on  the  edges  of  the  groove. 

27.  Side  Chisel. — The  side  chisel,  shown  in  Fig.  18  (/) 
and  (z/z),  is  used  for  finishing  the  sides  of  slots  and  similar 
work.  The  chisel  is  ground  straight  on  the  side  next  to  the 
work,  if  it  is  to  be  used  in  deep  holes;  for  shallow  holes  it  is 
best  to  give  it  a slight  angle,  as*  indicated  by  the  line  a b, 
Fig.  18  (zzz),  and  to  allow  the  body  of  the  chisel  to  stand  at 
a greater  angle  to  the  work  while  being  used. 


§20 


BENCH,  VISE,  AND  FLOOR  WORK. 


19 


The  proper  cutting  angle  for  most  of  the  chisels  mentioned 
above  is  practically  the  same  as  that  for  the  flat  chisel  for 
metals  of  the  same  grade,  the  angles  for  different  grades  of 
metal  varying  from  50°  to  75°.  The  softer  the  metal,  the 
sharper  the  chisel  should  be. 

Cold  chisels  are  often  used  in  the  pneumatic  hammer,  and 
when  so  used  the  shanks  must  be  fitted  to  the  holder  in  the 
hammer,  either  by  turning  or  milling,  and  the  head  should 
be  carefully  tempered  in  order  to  keep  it  from  being  upset 
in  the  socket  of  the  machine.  The  chisels  used  in  the  pneu- 
matic machine  should  be  longer  than  those  used  by  hand. 


CHIPPING. 

28.  Introduction. — Chipping  is  the  process  of  remov- 
ing stock  by  means  of  the  hammer  and  chisel.  It  corre- 
sponds to  the  roughing  cut  in  machine  tool  work,  and  the 
filing  that  follows  it  takes  the  place  of  the  finishing  cut. 

There  are  two  methods  of  chipping — the  hand  and  the 
pneumatic.  Chipping  is  a process  applied  to  the  roughest 
and  coarsest  work,  and  it  is  also  used  on  some  of  the  finest 
work  that  comes  to  the  machinist.  It  is  used  in  the 
machine  shop,  foundry,  and  smith  shop,  and  chisels  of  vari- 
ous sorts  form  an  important  part  of  the  outfit  of  the  erect- 
ing gang.  A heavy  chisel  fitted  with  a wooden  handle  is 
used  in  both  foundry  and  machine  shop,  for  removing  the 
largest  projections  and  fins  on  castings. 

29.  Holding  the  Hammer  and  Chisel. — For  ordi- 
nary chipping,  a hammer  weighing  from  1 to  If  pounds  is 
used,  and  a variety  of  chisels,  the  most  common  of  which 
are  the  flat,  cape,  gouge,  and  various  forms  of  side  and 
grooving  chisels.  When  chipping,  the  hammer  is  held  in 
the  right  hand,  as  shown  in  Fig.  19,  and  is  grasped  by  the 
thumb  and  second  and  third  fingers,  the  first  and  fourth 
fingers  being  closed  loosely  around  it.  This  method  of 
holding  the  hammer  handle  allows  it  to  be  swung  more 
Steadily  and  more  freely  without  tiring  the  hand  so  much  as 


20 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


would  be  the  case  if  the  handle  were  grasped  rigidly  by  all 
four  fingers.  The  chisel  should  be  grasped  in  the  left  hand 
with  the  head  close  to  the  thumb  and  first  finger.  The 
chisel  is  held  firmly  with  the  second  and  the  third  fingers, 
and  the  little  finger  may  be  used  to  guide  the  tool  as  may  be 
required.  The  first  finger  and  the  thumb  should  be  left 
slack,  as  they  are  then  in  a state  of  rest,  with  the  muscles 


Fig.  19. 


relaxed,  and  are  less  liable  to  be  injured  if  struck  with  the 
hammer  than  if  they  were  closed  rigidly  about  the  chisel. 
The  point  of  the  chisel  is  held  on  the  work,  as  shown  in 
Fig.  19,  at  the  place  where  it  is  desired  to  take  the  cut, 
before  the  hammer  blow  is  delivered,  and  at  an  angle  that 
will  cause  the  cutting  edge  to  follow  approximately  the 
desired  finished  surface.  After  each  blow  the  chisel  is  reset 
to  its  proper  position. 


BENCH,  VISE,  AND  FLOOR  WORK. 


21 


20 


EXAMPLES  OF  CHIPPING. 

30.  Piston-Valve  Hushing. — Fig.  20  is  an  illustra- 
tion of  one  class  of  bench  work;  a represents  the  bushing  of 
a piston  valve  in  which  two  series  of  ports  b and  c must  be 
cut  out  of  the  solid  metal  by  hand.  This  same  operation 
may  be  performed  more  economically  on  a milling  machine, 
but  it  is  frequently  done  by  hand.  The  ports  are  laid  out  in 
the  usual  way,  the  outline  d being  clearly  marked  on  the 


Fig.  20. 


painted  surface.  The  bushing  is  then  taken  to  the  drilling 
machine  and  the  ports  are  drilled  out,  just  enough  stock 
being  left  outside  of  the  drill  holes  to  insure  a good  finish. 
The  holes  may  be  drilled  so  close  together  that  when  the 
drilling  is  finished  the  block  of  metal  may  easily  be  removed 
by  a blow  with  the  hammer.  The  ridges  between  the  drill 
holes  are  chipped  away,  as  shown  in  the  illustration,  and  the 
sides  of  the  ports  are  finally  finished  to  the  lines  by  filing/ 


22 


BENCH,  VISE,  AND  FLOOR  WORK.  §20 


3 1 « Key  Seats. — Key  seats  in  pulleys  and  gears  are 
often  chipped  in.  They  are  first  laid  out  on  both  ends  of 
the  hub  and  lines  drawn  through  the  bore.  If  the  key  seat 
is  a narrow  one,  a chisel  of  corresponding  width  is  used,  and 
the  cut  driven  from  each  end ; but  if  the  seat  is  a wide  one, 
two  or  more  narrow  parallel  grooves  are  chipped  through, 
and  the  stock  between  is  removed  with  a flat  chisel. 

32.  Cutting  a Keyway. — The  manner  of  laying  out 
and  cutting  a key  seat  in  a shaft  is  as  follows:  The  key  seat 


is  first  laid  out  as  shown  by  the  lines  a b , c d,  ef,  Fig.  21  ( a ). 
The  lines  are  sometimes  marked  with  a prick  punch,  as  shown. 
The  side  lines  ab  and  c d of  the  key  seat  should  be  marked 
with  a deep  chisel  cut,  as  shown  at  a and  d in  the  end  view, 
to  prevent  the  material  from  tearing  out  along  the  sides  of 
the  keyway  during  the  first  cut  with  the  chisel.  This  cut  is 
best  if  made  with  a side  chisel  ground  and  held  in  the  manner 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


23 


shown  at  g,  Fig.  21  ( b ).  An  ordinary  flat  chisel  may  be 
used  for  this  mark,  if  ground  quite  thin  and  held  at  such  an 
angle  as  to  bring  one  of  its  cutting  sides  square  with  the  side 
line  d. 

A cape  chisel  of  proper  width  is  used  to  remove  the  stock, 
several  light  cuts  being  driven  through  the  key  seat,  as 
indicated  by  the  dotted  lines  in  Fig.  21  (a).  The  key  seat, 
if  long  or  at  the  end  of  the  shaft,  may  be  finished  by  filing, 
but  when  it  is  in  the  middle  of  the  shaft  this  is  impossible, 
and  the  finishing  must  be  done  with  chisels. 

It  is  sometimes  considered  easier  to  drill  out  the  stock 
before  chipping.  This  is  done  by  laying  out  and  drilling  a 
line  of  holes  like  that  marked  //,  Fig.  21  ( a ),  down  to  the 
right  depth  and  squaring  the  bottoms  with  a square-end 
drill  and  chipping  the  remaining  stock  to  the  lines.  This  is 
especially  applicable  to  large  key  seats. 

33.  Chipping  Large  Flat  Surfaces.-— Large  sur- 
faces, whether  flat  or  curved,  are  finished  by  chipping  in  the 


a 


Fig.  22. 


following  manner : The  piece  is  laid  out  as  shown  in  Fig.  22, 
the  lines  a b,  a c,  etc.  extending  around  the  work  in  such  a 
manner  as  to  outline  the  edges  of  the  required  surface.  In 
order  to  facilitate  the  starting  of  the  chisel  and  to  prevent 
the  breaking  off  of  the  stock  as  the  chisel  leaves  the  work,  it 
is  well  to  chamfer  the  front  and  back  edges,  as 'shown  at  a b 
andr  d.  The  stock  above  the  lines  a b,  c d,  etc.  is  removed 
by  first  cutting  grooves  e,  e across  the  surface,  leaving  the 
ridges  ft  f between.  These  ridges  are  subsequently  removed 


24 


BENCH,  VISE,  AND  FLOOR  WORK.  §20 


with  a flat  chisel.  In  the  illustration,  the  left-hand  ridge 
has  all  been  removed  and  half  of  the  one  next  to  it.  By 
cutting  the  grooves  across  with  the  cape  chisel,  the  work  of 
the  flat  chisel  is  much  reduced,  as  it  has  only  straight  cut- 
ting with  no  tearing  or  lifting  of  the  metal  at  the  corners. 
The  width  of  the  ridges  y is  determined  by  the  width  of  the 
flat  chisel  to  be  employed,  and  should  be  as  wide  as  the  char- 
acter of  the  material  being  cut  will  permit. 

34.  Chipping  Strip. — The  castings  for  boiler  fronts 
and  many  other  kinds  of  work  are  frequently  fitted  by  chip- 
ping and  filing.  Work  of  this  class  has  what  is  called  a 
chipping  strip  on  the  casting  wherever  fitting  is  to  be 
done.  This  strip  is  inch  or  more  higher  than  the  body  of 
the  casting,  and  wide  enough  to  make  the  joint  or  fit.  Cast- 
ings to  be  fitted  by  this  process  are  put  together  and  their 
high  spots  noted,  chalked,  and  chipped  off  As  the  work 
progresses  and  the  heavier  parts  are  removed,  red  marking 
is  rubbed  on  the  work,  and  the  parts  are  tried  or  rubbed 
together.  The  coating  of  red  will  be  rubbed  off  on  the 
spots  that  come  in  contact  with  the  other  part,  thus  show- 
ing more  plainly  where  the  chipping  must  be  done.  When 
the  parts  have  been  chipped  to  fit  approximately,  they  are 
finally  finished  by  filing. 

35.  Pneumatic  Hammer. — The  pneumatic  hammer 
illustrated  in  Fig.  23  is  sometimes  used  for  chipping,  and  has 


Fig.  23. 


some  advantages  over  the  hand  method.  It  is  supplied  with 
air  at  a pressure  of  about  80  pounds  per  square  inch,  through 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


25 


a small  hose  connected  to  the  hammer  at  a.  The  operator 
holds  the  chisel  b,  which  has  a hexagonal  shank  fitting  a 
similarly  shaped  socket  in  the  machine,  in' his  left  hand,  as  in 
ordinary  chipping,  and  the  machine  is  held  by  the  handle  c 
in  his  right  hand,  with  the  thumb  on  the  trigger  e.  The 
whole  is  held  firmly  in  position  against  the  work,  and  light 
pressure  applied  to  the  trigger  to  start  the  chisel  into  the 
metal.  As  soon  as  the  cut  is  started,  more  air  may  be 
admitted  to  the  tool,  making  it  strike  harder  and  faster. 
The  blows  struck  by  this  hammer  are  so  rapid  that  the 
chisel  has  almost  a continuous  cutting  motion.  Heavy  or 
light  blows  may  be  struck,  as  the  operator  desires,  by  regu- 
lating the  pressure  of  the  thumb  upon  the  trigger. 

Pneumatic  machines  of  this  type  are  used  for  many  pur- 
poses, and  have  round  instead  of  hexagonal  bushings  for 
holding  the  chisel.  The  chisel  with  the  hexagonal  shank  is 
easily  guided  by  the  handle  c of  the  machine,  but  the  round- 
shanked  chisel  must  be  guided  by  the  left  hand.  The  tool 
shown  at  d is  used  for  beading  boiler  flues  and  similar  work. 

36.  Die  Sinking. — Die  sinkers  do  a great  deal  of  chip- 
ping in  finishing  their  dies.  All  the  stock  that  can  be  is 
removed  by  some  form  of  machining,  and  the  inaccessible 
parts  are  chipped  with  special  chisels  and  finished  by  filing 
and  scraping. 

37.  Making  Bottle  Molds. — The  lettering  on  glass 
bottles  is  made  by,  letters  cut  into  the  bottle  mold.  The 
letters  are  marked  off  in  the  mold  and  then  the  operator 
chips  them  out,  using  a hammer  weighing  about  4 ounces. 
The  main  parts  of  the  letters  are  formed  by  a V or  diamond- 
shaped chisel,  like  the  one  shown  in  Fig.  18  (/i)  and  (/). 
During  this  portion  of  the  work  the  chisel  is  driven  ahead, 
as  in  ordinary  chipping;  but  to  form  the  ends  of  the  molds, 
the  chisel  is  held  in  an  upright  position  and  driven  down- 
wards. A graving  tool  is  used  to  smooth  the  letters,  and 
bent  or  half-round  files  are  used  for  smoothing  the  surface 
of  the  mold. 


20 


BENCH,  VIvSE,  AND  FLOOR  WORK.  § 20 


FILES  AND  FILING. 


INTRODUCTION. 

38,  Use  of  Files. — In  finishing  machine  parts,  there 
are  many  cases  where  a smaller  reduction  in  size  or  a more 
perfect  surface  is  required  than  can  be  obtained  by  the  use 
of  machine  tools  or  by  chipping.  Files  are  used  for  either 
of  these  purposes,  for  by  their  careful  and  skilful  use  great 
accuracy  can  be  obtained.  In  order  to  make  a rough  sur- 
face smooth,  files  of  various  degrees  of  fineness  are  used,  a 
coarse  one  first,  followed  successively  by  finer  grades,  the 
piece  being  finished  with  the  finest. 

39.  Elementary  Principle. — A file  is  made  of  a piece 
of  steel  of  the  desired  shape  and  size,  and  has  a series  of 
grooves  cut  across  its  face.  When  a file  is  passed  over  the 
surface  of  a body  of  metal  or  other  material,  the  teeth 
formed  by  the  grooves  act  on  it  as  a series  of  small  chisels, 
each  removing  a small  chip.  By  passing  the  file  across  the 
surface  successively,  the  high  parts  are  removed.  Each  file, 
however,  leaves  its  own  marks,  and  these  are  removed,  if 
desired,  by  means  of  the  finer  grades. 


DEVELOPMENT  OF  FILES. 

40.  Hand-Cut  Files. — Formerly,  all  files  were  cut  by 
hand  with  flat  chisels,  the  spacing  being  gauged  by  the  eye, 
shape  of  chisel,  and  weight  of  hammer  blow.  The  steel 
from  which  they  were  made  was  forged  to  the  required 
shape,  with  a tang  on  which  to  fasten  a handle.  The  piece 
was  then  carefully  annealed,  after  which  it  was  ground  and 
cut.  The  hardening  was  usually  done  by  covering  the  file 
with  a coating  of  some  substance  that  protected  the  teeth 
from  the  action  of  the  heat,  but  permitted  the  body  to  be 
heated  to  a temperature  that  would  give  the  proper  hardness 
when  the  file  was  plunged  into  a bath  of  oil  or  water. 

41.  Machine-Cut  Files. — On  account  of  the  expense 
of  hand  cutting,  various  methods  of  cutting  with  machines 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK.  27 

have  been  tried,  with  varying  degrees  of  success.  The  first 
machine-cut  files  were  cut  with  regularly  spaced  teeth. 
There  are  serious  objections  to  this  style  of  files,  since,  in 
filing,  the  teeth  follow  each  other  at  regular  intervals  and 
drop  into  the  cuts  made  by  the  preceding  ones,  causing 
chattering.  The  hand-cut  files  are  more  satisfactory,  as  the 
slight  irregularity  in  the  spacing  is  sufficient  to  prevent  the 
chattering.  This  difficulty  in  machine-cut  files  was  over- 
come by  a few  makers  by  two  methods.  It  was  found  that 
by  increasing  the  spaces  between  the  teeth  gradually  from 
the  end  to  the  middle,  and  again  decreasing  as  the  other 
end  is  approached,  enough  variation  may  be  produced  to 
preveat  the  chattering,  without  causing  enough  change  from 
the  true  spacing  to  affect  the  working  conditions.  By  this 
method  of  cutting,  called  the  increment  cut , the  two  ends 
of  the  file  are  of  the  same  coarseness,  while  the  middle  is 
somewhat  coarser. 

Files  are  also  cut  with  the  gradations  of  spacing  running 
from  one  end  to  the  other,  the  spacing  being  finer  at  the 
point  and  increasing  gradually  to  the  shoulder,  thus  accom- 
plishing practically  the  same  result  as  in  the  style  mentioned 
above.  This  is  also  known  as  an  increment  cut. 

Chattering  is  also  prevented  by  cutting  the  teeth  slightly 
out  of  parallel.  By  changing  the  direction  of  the  deflection 
several  times  in  the  length  of  the  file,  enough  variation  may 
be  obtained  to  avoid  this  trouble.  Files  cut  in  this  way  are 
largely  used  at  the  present  time. 

It  has  been  found  that  by  varying  the  angle  of  the  motion 
of  the  file  gradually  during  the  forward  stroke,  when  there 
is  a tendency  to  chatter,  the  regularly  spaced  file  will  work 
smoothly  and  well,  and  hence  this  style  of  file  is  still  used  in 
many  shops. 


DEFINITION  OF  TERMS. 

42.  The  following  definition^  are  taken  almost  in  their 
entirety  from  “ Filosophy,”  one  of  the  publications  of  the 
Nicholson  File  Company. 


28 


BENCH,  VISE,  AND  FLOOR  WORK. 


20 


Back. — A term  commonly  used  to  describe  the  convex 
side  of  half-rounds,  cabinets,  pitsaws,  and  other  files  of 
similar  cross-sectional  shape. 

Bellied. — A term  sometimes  used  to  describe  a file  having 
a fulness  in  the  center. 

Blunt. — A term  applied  in  describing  files  that  preserve 
their  sectional  shape  throughout,  from  point  to  tang , as 
shown  in  Fig.  24  ( a ). 


(a) 


Co) 

Fig.  24. 


Equaling. — A term  applied  to  describe  a blunt  file  upon 
which  is  produced  an  exceedingly  slight  belly,  or  curvature, 
extending  from  point  to  tang , the  file  apparently  remaining 
blunt. 

Filing  Block. — A piece  of  hard  close-grained  wood,  having 
grooves  of  varying  sizes  on  one  or  more  of  its  sides.  It  is 
usually  attached  to  the  work  bench  by  a small  chain,  and 
when  grasped  in  the  jaws  of  a vise  is  particularly  useful  in 
holding  small  rods,  Avires,  or  pins  that  are  to  be  filed;  also 
in  filing  small  flat  pieces  that  are  held  on  the  block  by  pins 
or  by  letting  in. 

Float. — The  coarser  grades  of  single-cut  files  are  not 
infrequently  called  floats  when  cut  for  the  plumber’s  use  or 
for  use  on  soft  metals  or  wood. 

Hopped. — A term  known  among  file  makers,  and  used  to 
represent  a very  coarse,  or  open , spacing  of  the  teeth  (some- 
times exceeding  inch),  mostly  applied  to  the  backs  of  half- 
rounds  and  to  the  edges  of  quadrangular  sections. 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


29 


Middle  Cut. — A term  used  to  designate  the  cut  of  a file 
when  it  is  of  a grade  of  coarseness  between  the  rough  and 
the  bastard.  It  is  but  little  used  in  this  country. 

Recut,  or  Recutting. — The  working  over  of  old  or  worn-out 
files  by  the  several  processes  of  annealing,  grinding  out  the 
old  teeth,  recutting,  hardening,  etc.,  and  thus  again  prepar- 
ing them  for  use.  This  operation  is  sometimes  repeated  two 
and  even  three  times;  but  the  economy  of  recutting  at  all  is 
very  much  questioned,  and  the  practice  is  done  away  with 
in  most  of  the  best  shops  of  the  present  day. 

Safe  Edge  (or  Side). — Terms  used  to  denote  that  a file 
has  one  or  more  of  its  edges  or  sides  smooth  or  uncut,  that 
it  may  be  presented  to  the  work  without  injury  to  that  por- 
tion which  does  not  require  to  be  filed. 

Scraping. — As  applied  in  machine  shops,  the  process  con- 
sists of  removing  an  exceedingly  small  portion  of  the  wearing 
surfaces  of  machinery  by  means  of  scrapers,  in  order  to 
bring  these  surfaces  to  a precision  and  nicety  of  finish  (as 
determined  by  the  straightedge  or  surface  plate)  not  attain- 
able by  the  file  or  by  any  other  means  with  which  we  are 
acquainted. 

Superfine  (or  Super ) Cut. — A term  applied  by  the  Lanca- 
shire file  makers  to  designate  a.  grade  of  cut  known  in 
America  as  “ dead  smooth.” 

Taper.— This  term  is  used  to  denote  the  shape  of  the  file 
shown  in  Fig.  24  (b),  as  distinct  from  blunt.  Custom  has 
also  established  it  as  a short  name  for  the  three-square, 
or  triangular,  hand-saw  file. 


DISTINGUISHING  FEATURES. 

43.  Character  of  Cut. — The  teeth  of  files  are  not 
generally  cut  at  right  angles  to  the  sides  of  the  file,  but  are 
set  at  an  angle,  as  shown  in  Fig.  25.  This  angle  varies  for 
different  materials.  Files  used  in  machine  shops  are  cut  in 
two  different  ways,  known  as  single-cut  and  double-cut. 


30 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


44.  Single-Cut. — Single-cut  files  are  cut  with  a 

single  series  of  teeth  running  continuously  from  one  end  of 
the  file  to  the  other,  as  illustrated  in  Fig.  25  ( a ).  They 


(a) 


(b) 

Fig.  25. 


are  used  almost  entirely  for  filing  in  lathes,  and  for  the 
softer  materials,  such  as  lead,  wood,  horn,  etc.  The  coarser 
grades  are  often  called  floats. 

45.  Double-Cut. — Single-cut  files  are  rarely  used  in 
the  machine  shop,  except  on  lathe  work  or  on  brass.  By 
making  another  cut,  at  an  angle  to  the  first,  or  over-cut,  a 
file  is  produced  as  shown  in  Fig.  25  ( b ),  and  is  called  a 
double-cut.  The-  second,  or  up-cut , is  generally  cut  a little 
finer  and  not  as  deeply  as  the  over-cut.  The  angles  that 
the  two  cuts  make  with  the  axis  of  the  file  vary  for  different 
uses,  the  over-cut  ranging  from  35°  to  55°,  and  the  up-cut 
from  75°  to  85°.  The  up-cut  has  the  effect  of  dividing  the 
small  cutting  edges  produced  by  the  over-cut  into  a large 
number  of  small  pointed  teeth.  Files  thus  made  in  various 
grades  of  coarseness  give  excellent  results  on  the  ordinary 
materials  used  in  machine  construction. 

46.  Coarseness  of  Cut.  — American  practice  has 
divided  machine-shop  files  into  the  following  classes,  with 
regard  to  their  coarseness : 

Single-Cut. — Rough,  coarse,  bastard,  second  cut,  and 
smooth. 

Double-Cut. — Coarse,  bastard,  second  cut,  smooth,  and 
dead  smooth. 


§20 


BENCH,  VISE,  AND  FLOOR  WORK. 


31 


The  coarse  and  bastard  cuts  are  used  almost  entirely  on 
the  coarser  grades  of  work,  and  the  second  cut  and  smooth 


Pig.  26. 


are  used  in  finishing  and  for  the  finer  classes  of  work.  The 
rough  and  dead  smooth  are  rarely  used  in  the  machine  shop, 


32 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


although  occasionally  a rough  single-cut  may  be  required 
where  much  work  in  lead  or  other  soft  material  is  necessary. 
The  dead-smooth  double-cut  is  occasionally  used  on  extremely 
fine  work,  but  it  is  required  so  rarely  that  many  good 
mechanics  never  have  occasion  to  use  one. 

The  coarseness  of  the  cut  for  each  grade  varies  with  the 
size  of  file,  the  cut  being  coarser  on  the  larger  files.  Fig.  26 
shows  the  comparative  coarseness  of  4-inch  and  16-inch  files, 
(a),  (b),  (c),  and  ( d ) showing  the  single-cut,  rough,  coarse, 
bastard,  and  second  cut,  and  (c),  (/),  (g),  and  (k)  the 
double-cut,  coarse,  bastard,  second  cut,  and  smooth. 


STYLES  OF  FILES. 

47.  Files  are  divided  into  three  general  classes  with 
regard  to  their  cross-sections,  viz.  : quadrangular , circular , 
and  triangular . Besides  these,  there  are  some  other  mis- 
cellaneous cross-sections,  but  they  are  not  used  in  machine 
shops,  and  will  therefore  not  be  considered  here. 

The  accompanying  table,  which  is  taken  almost  entirely 
from  ‘ ‘ F ilosophy,  ” shows  the  machine-shop  files  classed  under 
these  various  headings,  with  their  description  and  machine- 
shop  uses,  the  first  column  showing  the  cross-section  of  each 
style.  Many  of  these  are  used  for  other  purposes  than  those 
mentioned,  only  their  application  to  machine-shop  work 
being  mentioned  here. 

SIZES  OF  FILES. 

48.  The  size  of  a file  is  generally  indicated  by  giving 
the  length  in  inches  of  the  cut  part,  the  tang  not  being 
included.  Thus,  a 10-inch  bastard  flat  file  means  a bastard 
flat  file  10  inches  long  from  the  point  of  the  file  to  the  tang. 


BRITISH  CLASSIFICATION  OF  FILES. 

49.  The  classification  of  files  in  Great  Britain  differs 
slightly  from  the  American  classification;  while  the  files  of 
the  two  principal  British  makes,  the  Sheffield  and  the  Lan- 
cashire, are  slightly  different.  The  naming  of  the  Sheffield 


§20 


BENCH,  VISE,  AND  FLOOR  WORK. 


o 

o 


3 


c.  S.  III.— It 


34 


BENCH,  VISE,  AND  FLOOR  WORK. 


20 


files  with  regard  to  their  coarseness  is  as  follows:  rough, 
middle,  bastard,  second  cut,  smooth,  and  dead  smooth. 
The  finest  grade  of  the  Lancashire  files  is  called  “ superfine,” 
instead  of  ‘ ‘ dead  smooth.  ” It  will  be  seen  that  the  ‘ ‘ middle” 
corresponds  to  the  American  “ coarse.” 

The  degrees  of  coarseness  represented  by  these  various 
names  in  the  Sheffield,  Lancashire,  and  American  classi- 
fications differ  somewhat,  but  not  enough  to  cause  any 
material  difference  in  the  working  conditions.  A remark- 
able degree  of  fineness  of  cut  has  been  attained,  Lanca- 
shire superfine  hand-cut  files  of  the  smallest  size  having 
been  made  with  300  cuts  to  the  inch. 


FILING  OPERATIONS 

50.  Purpose  of  Filing.  — In  machine  construction 
there  are  many  instances  where  parts  must  be  finished  by 
hand.  The  part  may  have  been  finished  as  far  as  possible 
in  a machine  tool,  but  the  surface  could  not  be  made  suffi- 
ciently smooth,  and  must  be  finished  by  hand;  or  it  may  be 
so  located,  or  of  such  a character,  that  a machine  tool  can- 
not be  used,  and  the  entire  work  must  be  done  by  hand.  In 
the  latter  case,  the  excess  of  metal  may  be  removed  with  a 
cold  chisel,  and  the  work  then  finished  by  filing. 

It  has  already  been  said  that  a file  consists  of  a series  of 
minute  chisels  that  are  passed  over  the  work  by  hand,  under 
a pressure  that  is  just  great  enough  to  make  them  cut.  For 
rough  work,  the  coarser  grades  of  files  are  used ; and  as  the 
surface  becomes  smoother,  finer  grades  are  used  successively. 

51.  Difficulties  to  Contend  With. — The  operation 
of  filing  is  one  of  the  most  difficult  of  machine-shop  opera- 
tions, and  the  quality  of  the  work  produced  depends  almost 
entirely  on  the  skill. of  the  workman.  In  most  machine- 
shop  operations,  the  tool  is  guided  positively  by  some  pro- 
vision in  the  machine  with  which  the  operation  is  performed, 
as  in  a planer,  shaper,  or  milling  machine.  In  filing,  the 
accuracy  of  the  work  depends  entirely  on  the  motion  of  the 
hands,  without  any  means  of  guiding  the  tool  positively. 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


35 


It  will  be  seen,  therefore,  that  skilfulness  on  the  part  of 
the  workman  is  essential  to  good  work,  the  quality  of  the 
file  being  of  secondary  importance.  A poor  workman  may 
be  provided  with  a good  file,  but  his  work  will  not  be  good, 
while  a good  workman  may  do  very  good  work  with  a poor 
tool.  In  order  to  do  the  best  work,  however,  it  is  neces- 
sary to  have  a good  file  that  is  adapted  to  the  work  to  be 
done. 

52.  Advantage  of  Convex  Faces  in  Files. — To  the 

unskilled  it  would  seem  at  first  thought  that  a file  having  a 
perfectly  straight  surface,  bearing  on  the  work  equally  at 
all  points,  is  essential  in  order  to  do  good  work.  A little 
experience  will  show  that  this  is  not  true,  and  that  a sur- 
face that  is  slightly  convex  will  produce  better  results.  In 
filing,  the  pressure  of  the  hands  is  put  on  the  two  ends  of 
the  file,  with  the  result  that  the  spring  thus  caused  tends  to 
make  the  lower  face  concave;  also,  when  files  are  being 
hardened,  they  have  a tendency  to  spring,  thus  making 
it  impossible  to  produce  files  that  have  perfectly  straight 
surfaces. 

In  filing  wide  surfaces,  a perfectly  straight  file  would 
require  a very  heavy  pressure  to  make  it  bite  (take  a cut) ; 
while  the  same  file  on  a narrow  surface  would  bite  under  a 
very  light  pressure.  In  the  latter  case,  the  pressure  is  con- 
centrated on  a few  teeth;  while  in  the  former  it  is  dis- 
tributed over  a large  number,  and  in  order  to  secure  enough 
pressure  on  each  tooth  to  make  it  cut,  a very  heavy  pressure 
is  necessary.  It  is  found  in  practice  that  a light  pressure 
with  a small  number  of  teeth  in  contact  will  produce  the 
best  results.  By  making  the  files  convex,  only  a few  teeth 
will  be  in  contact  at  one  time,  however  wide  the  surface  may 
be.  The  faces  of  files  are,  therefore,  made  convex  for  three 
reasons:  to  overcome  the  effect  of  spring  due  to  the  pres- 
sure of  the  hands,  to  overcome  the'spring  caused  by  harden- 
ing, and  to  make  the  file  bite  on  any  width  of  surface. 

53.  Wooden  File  Handles. — File  handles  are  gen- 
erally made  by  turning  a piece  of  wood  to  the  desired  shape, 


36 


BENCH,  VISE,  AND  FLOOR  WORK.  §20 


putting  a ferrule  on  the  end,  and  drilling  a hole  into  it  to 
receive  the  tang  of  the  file.  As  the  sizes  of  the  tang  vary 
for  the  different  forms  and  sizes  of  files,  the  hole  must  be 
small  enough  to  receive  the  smallest  file  for  which  it  is 
intended.  If  the  handle  is  made  of  a soft  wood,  the  larger 
tangs  may  be  driven  in  without  splitting  it ; but  when  made 
of  hard  wood,  it  is  necessary  to  enlarge  the  hole  to  about 
the  right  size.  This  may  be  done  by  heating  the  tang  of  a 
worn-out  file  of  the  same  size  as  the  one  being  filed,  and 
burning  out  the  hole  in  the  handle.  If  no  old  file  is  avail- 
able, the  tang  of  the  new  file  may  be  heated,  but  care  must 
be  taken  that  the  temper  of  the  file  is  not  drawn.  This 
may  be  prevented  by  wrapping  a piece  of  wet  waste  about 
the  file  up  to  the  tang.  The  handle  should  be  driven  well 
up  to  the  heel  of  the  file. 

54.  Special  File  Handles.- — In  filing  broad  surfaces, 
as  the  tops  of  lathe  beds,  and  in  finishing  long  slots,  the 
ordinary  wooden  handle  cannot  be  used  and  other  devices 
have  been  brought  into  use.  Fig.  27  shows  a simple  handle 


that  has  been  found  very  efficient.  The  end  a is  formed 
with  a dovetailed  slot  that  slips  over  the  tang,  while  the 
point  b rests  upon  the  back  of  the  file.  The  slot  should  be 
made  to  fit  about  the  middle  of  the  tang  of  a 12-inch  file. 
The  foot  a should  be  about  1|  inches  long  and  the  handle 
about  -|  inch  in  diameter. 

Another  device  that  is  frequently  used  and  that  has  some 
advantage  over  the  one  just  described  is  shown  in  Fig.  28. 
A foot  a rests  upon  the  file  and  has  a dovetailed  slot  that 
catches  over  the  tang.  A rod  b has  a lug  c on  its  front  end 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK.  37 

that  catches  over  the  point  of  the  file.  The  handle  d con- 
tains a nut  that  screws  on  the  end  of  the  rod  b,  and  by 


means  of  which  the  file  is  held  firmly  between  the  catch  c 
and  the  foot  a.  A column  e at  about  the  middle  of  the  file 
makes  the  device  more  rigid,  and  prevents  the  file  from 
springing  up  in  the  middle  when  pressure  is  put  upon  it.  A 
projection  on  the  front  end  of  the  rod  furnishes  a convenient 
thumb  rest.  This  device  is  used  quite  largely  and  has  given 
excellent  satisfaction. 


Fig.  29. 

55.  Holding  the  File.  — It  is  very  important  for  a 
beginner  to  acquire  the  correct  manner  of  holding  the  file. 


BENCH,  VISE,  AND  FLOOR  WORK. 


20 


38 


A right  way  is  learned  as  easily  as  a wrong  one,  but  having 
once  become  accustomed  to  the  wrong,  it  is  very  hard  to 
change  to  the  right.  There  is  some  difference  of  opinion 
as  to  the  correct  way,  but  the  following  is  considered  good 
practice. 

In  moving  the  file  endwise  across  the  work,  commonly 
called  cross-filing , it  is  generally  held  as  shown  in  Fig.  29  (a) 
and  (l?) ; for  the  lighter  grades  of  work,  and  in  finishing  cuts, 
the  former  illustration  shows  the  relation  of  the  hands  to  the 
file  at  the  beginning  of  the  stroke,  and  the  latter  at  the  end 
of  the  stroke.  The  point  of  the  file  is  held  between  the  thumb 
and  the  first  finger,  as  shown  in  the  two  views,  while  the 
handle  is  held  by  resting  the  thumb  upon  it,  as  shown  in  these 


illustrations  and  in  Fig.  30,  and  letting  the  end  stand  against 
the  palm  of  the  hand,  the  fingers  gripping  it  lightly.  When 
the  work  is  heavy  and  a large  file  is  used,  the  ball  of  the  left 
hand  is  placed  on  the  point  of  the  file,  while  the  handle  may 
be  gripped  as  shown  in  Fig.  30.  It  will  be  observed  that  in 
the  latter  case  the  handle  is  gripped  a little  farther  forwards 
than  in  the  case  of  light  work. 

56.  When  the  file  is  very  thin,  there  is  great  danger  of 
springing  it  so  as  to  round  the  corners.  This  may  be  pre- 
vented by  holding  it  as  shown  in  Fig.  31.  A downward 
pressure  is  put  upon  both  thumbs  and  an  upward  pressure 
upon  the  fingers  of  both  hands.  This  pressure  is  just  suffi- 
cient to  overcome  the  tendency  of  the  ends  to  spring  down- 
wards. By  making  the  pressure  great  enough  to  spring  the 
file  downwards  considerably  in  the  center,  a slightly  concave 
surface  may  be  formed. 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


39 


It  is  very  difficult,  however,  to  hold  a file  in  this  way  for 
more  than  a few  minutes,  and  it  is  better  to  use  a heavier 


Fig.  31. 


file  that  has  considerable  convexity  and  stiffness,  whenever 
that  is  possible.  On  very  light  files  spherical  handles  are 
often  used. 


57.  For  internal  work,  when  the  hole  is  long,  it  may  not 
be  possible  to  hold  the  file  at  the  point.  In  this  case  a very 
great  stress  comes  on  the  wrist  of  the  right  hand,  which 


40 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


soon  becomes  tired.  This  stress  may  be  relieved  by  placing 
the  left  hand  over  the  right,  as  shown  in  Fig.  32.  When  the 

work  is  thin,  so  that  the  file  will 
reach  through  the  work  far  enough 
to  take  hold  of  the  point,  the  ordi- 
nary method  of  holding  it  for  out- 
side work  is  generally  used.  In 
draw-filing,  the  file  is  grasped  at  each 
side  of  the  work,  as  shown  in  Fig.  33. 


Fig.  33. 


58.  Using  the  File. — Cross- 
filing, though  the  most  common,  is 
one  of  the  most  difficult  forms  of 
filing.  In  moving  the  file  back  and 
forth,  there  is  a tendency  for  the 
hands  to  swing  in  arcs  of  circles 
about  the  joints  of  the  arms,  while 
the  body  sways  more  or  less,  depend- 
ing on  the  work.  To  pvercome  these 
tendencies  so  as  to  move  the  file  in  straight  lines  requires 
a great  deal  of  practice  and  careful  observation  of  the 
results  of  certain  movements.  Filing  on  narrow  work  is 
especially  difficult.  The  work  becomes  a fulcrum  on  which 
the  file  rests  at  different 
points  along  its  course, 
and  if  an  equal  pressure 
is  put  on  each  end,  it 
will  tilt  first  one  way, 
then  another,  depend- 
ing on  the  point  of  con- 
tact and  the  leverage. 

For  instance,  in  Fig.  34,  when  the  file  is  in  position  a , there 
is  a tendency  for  the  handle  to  tilt  downwards  from  the  ful- 
crum b ; when  in  the  position  cf  represented  by  the  dotted 
lines,  the  point  tilts  downwards  about  the  fulcrum  d.  As 
the  file  runs  forwards,  there  is,  therefore,  a tendency  to  file 
off  the  corners  more  than  the  middle  of  the  piece  and  to 
produce  a convex  surface.  On  wide  work  there  is  less 


Fig.  34. 


20 


BENCH,  VISE,  AND  FLOOR  WORK. 


41 


tendency  to  do  this,  and  the  beginner  should,  therefore,  take 
his  first  lessons  on  work  ranging  between  about  1 inch  and 
4 inches  in  width.  By  persistent  care  to  have  the  file  rest 
evenly  upon  the  work,  he  may  entirely  overcome  this  diffi- 
culty, and  not  until  he  has  accomplished  this  should  he 
attempt  to  file  narrow  work. 

59.  Filing  Broad  Surfaces. — In  filing  broad  sur- 
faces, the  danger  of  rounding  the  corners  is  reduced  to  a 
minimum,  but  other  difficulties  present  themselves.  Files 
for  this  class  of  work  have  convex  faces,  and  only  a few 
teeth  cut  at  a time.  The  strokes  must  then  be  so  gauged 
that  an  equal  cut  is  carried  across  the  entire  piece.  It  is 
evident  that  if  numerous  short  strokes  are  made  they  are 
liable  to  overlap  each  other  at  some  places  and  not  meet  at 
others,  and  to  wear  out  the  files  at  the  middle  while  the 
ends  are  still  good.  Uniform  strokes  of  as  great  a length  as 
possible  should  be  made. 

When  high  spots  are  to  be  removed,  the  file  must  be  so 
held  that  the  teeth  over  these  spots  are  in  contact  with  the 
work.  By  commencing  the  'stroke  with  the  teeth  near  the 
point  in  contact,  and  lowering  the  handle  gradually  to  com- 
pensate for  the  convexity,  the  effective  work  of  the  whole 
stroke  may  be  concentrated  upon  a small  area.  On  the 
other  hand,  care  must  be  taken  so  that  this  is  not  done  when 
it  is  desired  to  remove  the  metal  evenly  from  a broad  sur- 
face, or  a concave  or  irregular  surface  will  be  the  result. 
In  this  case  the  file  should  move  perfectly  parallel  to  the 
work,  or  be  gradually  tilted  so  as  to  increase  the  length  of 
the  cut.  Great  care  should  be  taken  in  all  filing  opera- 
tions, and  by  constant  practice  the  correct  way  of  doing  the 
work  will  be  acquired  and  become  second  nature;  whereas 
a continuous  disregard  of  the  correct  methods  will  cause  the 
incorrect  manner  to  become  habitual. 

BO.  Diagonal  Filing. — It  will  be  noticed  in  filing  that 
small  grooves  are  left  upon  the  work  at  each  stroke,  and  when 
the  strokes  are  all  made  in  the  same  direction  these  grooves 


42 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


become  deeper;  this  increases  the  work  that  is  to  be  done, 
for  these  marks  must  be  removed  by  means  of  finer  grades 
of  files.  By  changing  the  angle  of  the  direction  of  the  stroke 
with  the  work,  at  short  intervals,  this  difficulty  may  be 
avoided.  This,  too,  will  make  the  file  cut  more  freely,  since 
the  grooves  running  at  an  angle  to  the  cut  cause  the  file  to 
bite  more  freely  and  the  particles  to  be  separated  more  easily. 
It  will  also  enable  the  workman  to  see  where  the  file  is  cut- 
ting and  to  gauge  the  stroke  so  that  the  desired  part  of  the 
surface  will  be  removed. 

Changing  the  course  of  the  file  as  described  above  is  often 
called  diagonal  filing.  The  angle  that  the  strokes  should 
make  with  each  other  depends  on  the  work.  Practice  alone 
will  enable  one  to  determine  what  it  should  be. 

61.  Pressure  on  File. — In  all  kinds  of  filing  there 
should  be  just  enough  pressure  put  upon  the  file  during  the 

forward  stroke  to  make 
it  cut  freely ; but  there 
should  be  no  pressure 
put  upon  it  during  the 
return  stroke.  The 
teeth  of  a file  are 
formed  approximately 
as  shown  enlarged  in  Fig.  35.  It  will  be  seen  that  when 
pressure  is  put  upon  the  file,  and  it  is  moved  in  the  direction 
of  the  arrow  a , the  cutting  edges  are  well  supported,  and 
the  angle  of  the  cutting  face  and  the  clearance  produce  very 
good  cutting  conditions.  When  moving  in  the  direction  of 
the  arrow  b,  which  corresponds  to  the  return  stroke,  the 
conditions  are  reversed.  The  angles  are  such  that  the  teeth 
will  simply  drag  over  the  work,  without  cutting,  while  the 
edges  are  not  well  supported,  and  any  pressure  put  upon 
the  file  will  cause  the  teeth  to  wear  away  very  rapidly  with- 
out producing  any  effect  upon  the  work.  In  fact,  the  cutting 
edges  of  some  of  the  teeth  of  a new  file  may  be  broken  the 
first  minute  the  file  is  used,  and  these  teeth  never  do  any 
work  again. 


BENCH,  VISE,  AND  FLOOR  WORK. 


43 


20 


a round 
possible 


fig.  36. 


(->2.  Filing  Curves. — In  filing  circular  holes, 
file  that  is  as  nearly  the  size  of  the  hole  as  it  is 
to  obtain  should  be  used.  A small 
file  will  tend  to  produce  the  ridges 
shown  in  Fig.  36;  with  a larger  file 
that  conforms  more  nearly  to  the  curva- 
ture of  the  hole,  this  tendency  is  greatly 
reduced.  When  the  filing  is  to  be  done 
on  an  internally  curved  surface  of  a 
large  radius,  as  shown  in  Fig.  37,  a 
half-round  file  is  used.  As  iri  the  case 
of  the  circular  hole,  there  is  a tendency  to  file  unevenly,  and 
a file  of  as  large  a curvature  as  is  obtainable  should  be  used. 

The  file  should  be 
7777777777?>.  ///////////z  moved  along  the  cir- 

cumference of  the 
curve  as  well  as  across 
the  work,  which  gives 
it  a diagonal  motion, 
and  in  addition  to  the 
advantages  of  diag- 
onal filing  on  flat  surfaces,  prevents  the  formation  of 
ridges. 


Fig.  37 


63.  Filing  Into  Corners. — When  it  is  necessary  to 
form  a sharp  corner,  or  to  file  up  to  a finished  surface  that 
stands  at  right  angles  to  the  one  on  which  the  filing  is  done, 
a safe-edge  file  is  used,  thereby  preventing  any  injury  to 
the  finished  part.  When  the  corner  is  to  be  extremely 
sharp,  a half-round  file  may  be  used,  or  a flat  file  may  be 
ground  off  on  one  side,  to  form  a safe  edge.  Either  the 
half-round  or  a flat  file  ground  in  this  way  has  a sharp  edge 
that  will  permit  a sharp  angle  to  be  formed.  Some  forms 
of  triangular  files  will  also  make  a sharp  corner.  The  other 
files  used  in  ordinary  work  are  so  cut  that  the  corners  are 
either  rough  or  slightly  rounded  and  will  not  make  a clean, 
sharp  angle.  When  the  corners  are  to  be  rounded,  a round- 
edge  file  will  give  good  results. 


44 


BENCH,  VISE,  AND  FLOOR  WORK. 


20 


04.  Filing  Slots  With  Curved  Ends. — For  filing  out 

slots  that  have  been  roughed  out  by  drilling,  and  where  the 
end  of  the  slot  is  to  be  rounded,  a flat,  round- 
edged  file  is  the  most  suitable.  When  the 
sides  have  been  machined  to  size  and  the 
end  of  the  slot  is  to  be  rounded,  a round  file 
with  the  sides  ground  off  to  the  width  of  the 
slot,  as  shown  in  Fig.  38,  may  be  used.  Two 
safe  edges  a and  b are  thus  formed  that  will 
prevent  injury  to  the  finished  sides. 

65.  Draw-Filing. — When  the  filing  is  done  by  moving 
the  file  sidewise  across  the  work,  it  is  called  draw-filing. 
Fig.  33  illustrates  how  the  file  is  held,  the  motion  being  at 
right  angles  to  its  length.  Draw-filing  is  used  very  gener- 
ally in  finishing  turned  work,  where  it  is  desired  to  remove 
the  circular  tool  marks  and  lay  the  marks  endwise.  Care 
should  be  taken  to  hold  the  file  so  that  the  teeth  will  cut  as 
it  moves  away  from  the  body,  and  to  relieve  the  pressure  on 
the  return  stroke,  as  in  cross-filing. 

In  draw-filing,  the  cut  is  not  so  deep  as  in  cross-filing,  the 
teeth  standing  at  such  an  angle  to  the  direction  of  motion 
that  a light  shearing  rather  than  a cutting  effect  is  pro- 
duced ; very  smooth  work  may  be  done  by  this  method.  A 
second-cut  or  smooth  file  is  best  suited  for  draw-filing.  On 
convex  surfaces  a flat  file  or  the  flat  side  of  a half-round  file 
may  be  used;  but  in  concave  work  a round  file  or  half-round 
file  will  give  the  best  results.  When  a large  amount  of 
metal  is  to  be  removed,  it  should  be  done  by  cross-filing,  as 
the  cut  in  draw-filing  is  so  light  that  a very  great  amount 
of  time  would  be  required  to  remove  it  by  this  method. 

66.  Finishing  Filed  Work. — When  a better  finish  is 
required  than  can  be  produced  by  draw-filing,  the  surface 
may  be  rubbed  with  fine  or  worn  emery  cloth  and  oil,  the 
cloth  being  wrapped  about  a file  or  a piece  of  wood,  which 
is  used  as  in  draw-filing.  The  strokes  should  be  made  suc- 
cessively along  the  circumference  of  a cylindrical  piece,  in 
order  that  the  finish  may  be  even.  When  a very  fine  finish 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


45 


is  required,  the  draw-filing  may  be  followed  by  cross-filing 
with  a dead-smooth  file,  after  Which  it  may  be  rubbed  with 
the  emery  cloth  in  the  direction  in  which  the  draw-filing 
was  done. 

67.  Position  of  Body  When  Filing. — No  attempt 
should  be  made  to  keep  the  body  rigidly  in  one  position 
while  filing,  especially  on  heavy  work.  A free,  easy  motion 
of  the  body,  in  the  direction  in  which  the  file  is  moving, 
permits  a greater  force  to  be  exerted  without  undue  strain. 
In  filing  right-handed,  the  workman  stands  with  his  left  foot 
toward  the  work,  and  as  the  file  is  moved  forwards,  a slight 
bending  of  the  left  knee  will  tend  to  throw  the  body  against 
and  upon  the  file,  thus  assisting  in  making  the  cut.  During 
the  return  stroke  the  knee  is  again  straightened  as  the  body 
returns.  A little  practice  will  show  the  extent  to  which 
this  motion  of  the  body  can  be  made  to  assist  in  the  work. 

68.  Height  of  Work. — The  height  of  the  work  largely 
depends  on  the  class  of  filing  that  is  to  be  done.  Ordinarily, 
the  surface  to  be  filed  should  be  about  as  high  as  the  elbow 
of  the  workman.  When  the  work  is  extremely  heavy  it 
should  be  set  somewhat  lower,  in  order  that  a greater  pres- 
sure may  be  put  upon  it.  If  the  vise  or  supporting  device 
is  too  high,  a foot-board  or  low  bench  may  be  used  to  stand 
upon.  The  feet  of  the  bench  should  be  set  flush  with  the 
ends  of  the  board,  in  order  to  prevent  tipping  when  stepping 
upon  the  ends. 

69.  Effect  of  Oil. — The  effect  of  oil  on  filing  varies 
greatly  with  different  metals  and  different  classes  of  work. 
In  finishing  broad,  smooth  surfaces  of  cast  iron,  the  presence 
of  oil  prevents  the  file  from  cutting,  and  causes  it  to  slip  over 
the  surface,  thus  wearing  off  the  sharp  points  of  the  teeth. 

On  cast  iron,  generally,  and  especially  on  the  class  of  work 
mentioned  above,  oil  should  never  be  used.  On  the  other 
hand,  it  may  be  advantageously  used  when  filing  wrought 
iron  and  steel,  and  other  hard  fibrous  materials,  especially 
in  finishing  surfaces,  when  the  file  is  new  and  sharp.  Oil 
prevents  the  file  from  scratching  and  cutting  too  deeply. 


46 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


Sometimes  the  teeth  are  filled  with  chalk,  either  dry  or 
mixed  with  oil;  this,  to  a great  extent,  prevents  the  filings 
from  clogging  between  the  teeth.  New  files  are  usually  sent 
from  the  factory  covered  with  oil,  to  prevent  their  rusting. 
For  work  in  which  oil  is  objectionable  this  must  be  removed, 
which  is  sometimes  done  by  first  rubbing  off  the  surplus  oil, 
then  coating  the  file  with  chalk  and  brushing  it  off  carefully. 

70.  Selection  and  Care  of  Files. — The  life  of  a file 
may  be  prolonged  very  materially  by  exercising  care  in 
selecting  a suitable  one  for  each  piece  of  work,  and  in  using 
it  properly.  A new  file  should  never  be  used  on  rough  cast 
iron  from  which  the  sand  and  scale  have  not  been  removed, 
nor  on  narrow  surfaces.  Both  these  conditions  tend  to 
break  and  dull  the  teeth.  A well-worn  file  will  do  excellent 
service  in  both  these  cases.  On  narrow  work,  a worn  file 
will  give  better  results  than  a new  one,  the  teeth  on  a new 
file  being  so  sharp  that  the  few  teeth  in  contact  will  enter  so 
deeply  that  they  are  liable  to  be  injured  and  to  scratch  the 
work.  A new  file  should  be  first  used  on  brass  or  wide  sur- 
faces on  smooth  cast  iron. 

The  files  most  commonly  used  in  the  machine  shop  are  the 
12-inch  and  14-inch  flat  and  half-round  bastard,  the  double- 
cut, and  the  12-inch  and  14-inch  single-cut.  The  other  files 
mentioned  are,  of  course,  needed  very  frequently  for  finish- 
ing, or  for  special  operations,  and  should  be  kept  in  stock. 

One  of  the  most  serious  troubles  to  contend  with  in  filing 
is  the  tendency  to  pin.  The  cuttings  clog  between  the 
teeth,  forming  hard,  sharp  “ pins  ” that  scratch  the  material. 


fig.  39. 


This  is  known  as  pinning , and  occurs  more  readily  in  some 
materials  than  in  others.  As  soon  as  the  slightest  indication 
of  pinning  is  observed,  great  care  should  betaken  to  prevent 
it.  The  teeth  should  be  carefully  cleaned.  Sometimes  this 


§ 20 


BENCH,  VISE,  AND  FLOOR  WORK. 


47 


may  be  done  by  rapping  the  file  against  a wooden  block  or 
the  work  bench,  or  by  rubbing  the  hand  over  it.  In  most 
cases  it  is  necessary  to  use  a wire  brush,  called  a file  card , 
shown  in  Fig.  39.  Vigorous  brushing  in  the  direction  of 
the  teeth  usually  removes  the  pins,  but  in  cases  where  the 
brush  will  not  remove  them,  a piece  of  soft  sheet  brass,  or 
copper  or  iron  wire  flattened  out  at  one  end,  may  be  used. 
The  end  is  pressed  crosswise  upon  the  teeth  and  moved  in 
the  direction  of  the  length  of  the  teeth.  Little  grooves  will 
be  cut  into  the  soft  metal,  forming  small  teeth  that  clean 
the  file  thoroughly. 

71.  Files  should  never  be  thrown  upon  one  another,  or 
upon  other  tools  or  hard  substances.  In  too  many  cases, 
files,  hammers,  cold  chisels,  wrenches,  and  tools  of  all  kinds 
are  thrown  into  a box  or  cupboard  promiscuously,  resulting 
in  injury  to  the  files  and  all  other  cutting  edges,  to  say 
nothing  of  the  careless  and  dilapidated  appearance  of  the 
place  and  the  time  wasted  in  trying  to  find  anything  that  is 
wanted.  A tool  box  or  cupboard  should  always  be  kept  in 
order.  There  should  be  “ a place  for  everything  and  every- 
thing in  its  place”  when  not  in  use.  Files  should  be  laid 
either  upon  shelves  or  in  a drawer  that  is  provided  with  small 
divisions  so  as  not  to  permit  them  to  rub  against  each  other. 
They  should  always  be  carefully  cleaned  before  they  are  put 
away,  and  kept  in  good  condition  so  as  to  be  ready  for  use 
when  they  are  required. 

72.  Filing  Jigs. — These  are  generally  used  in  the 
making  of  duplicate  parts,  and  in  a great  variety  of  oper- 
ations where  it  is  necessary  to  produce  accurate  work  by 
filing,  and  to  do  this  practically  independent  of  the  skill  of 
the  workman.  Such  jigs  usually  consist  of  hardened  steel 
blocks  fastened  to  the  work,  and  made  in  suitable  shapes  to 
guide  the  file  so  as  to  remove  the  stock  to  the  proper  form 
in  each  case.  The  file  will  glide  over  the  hardened  jig  prac- 
tically uninjured  and  cut  away  the  softer  metal  of  the  piece 
pf  work  which  projects  above  it, 


48 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


One  form  of  jig  is  shown  in  Fig.  40.  This  jig  is  used  in 
making  rectangular  slots  in  boring  bars,  etc.  It  consists  of 
a hardened  steel  block  <2,  having  a hole  for  inserting  the 


work  b\  a rectangular  slot  c of  the  dimensions  required  to 
be  made  in  the  work ; a series  of  holes  d at  right  angles  to 
the  slot  c and  circumscribed  by  a rectangle  same  as  c ; and 
a setscrew  e to  hold  the  jig  on  the  work. 

In  cutting  such  a slot  in  a bar,  the  jig  is  slipped  on  to  the 
proper  position  and  clamped  by  means  of  the  setscrew.  The 
holes  are  then  drilled  through  the  work,  those  in  the  jig 
serving  to  guide  the  drill.  The  setscrew  is  then  loosened 
and  the  jig  turned  90°,  bringing  the  rectangle  over  the 
holes  just  drilled.  A plugger  may  be  used  to  drive  out  some 
of  the  metal  between  the  holes,  after  which  a file  is  used  to 
bring  the  slot  to  the  form  of  that  in  the  jig. 

A better  way  is  to  move  the  jig  a half  hole  endwise,  then 
run  an  end  mill  through  each  hole  of  the  jig  to  remove  the 
metal  left  between  the  holes  by  the  drill;  the  slot  may  ther 
be  finished  by  filing  as  described  above. 


FITTING  KEYS. 

73.  Rectangular  Keys. — Keys  of  a square  or  rect- 
angular cross-section  are  generally  planed  or  milled  a little 
larger  than  the  size  of  the  key  seats  they  are  to  fill,  and  are 


20 


BENCH,  VISE,  AND  FLOOR  WORK. 


49 


then  filed  to  fit.  If  the  key  is  to  fit  top  and  bottom,  it 
should  be  filed  true  to  a surface  plate  and  made  of  such 
width  as  to  fill  sidewise  the  key  seats  in  both  shaft  and 
wheel.  The  corners  should  be  slightly  rounded,  as  well  as 
the  ends.  The  shaft  is  now  put  into  the  bore,  with  the  key 
seats  in  line.  Red  or  black  marking  should  be  put  on  the 
surfaces  of  the  key  seat,  and  the  key  driven  in  lightly  and 
taken  out  and  filed  where  it  shows  bearing  marks.  Care 
should  be  taken  not  to  drive  the  key  too  tightly  at  first,  as 
it  .is  easily  sprung  to  conform  to  the  inequalities  of  the  hole, 
and  will  show  a greater  bearing  than  it  should.  Care  must 
be  taken  not  to  drive  the  key  in  dry,  as  it  will  surely  cut. 
The  marking  applied  to  the  seat  is  sufficient  at  first,  and 
later  the  marking  material  may  be  put  on  the  key,  where  it 
serves  the  double  purpose  of  marker  and  lubricant.  By 
repeated  trials,  the  key  is  brought  to  fit  the  seat  perfectly, 
and  then  may  be  driven  home  without  danger  of  throwing 
the  work  out  of  true. 

A well-fitted  hub  and  shaft  may  be  forced  considerably 
out  of  true  by  driving  a key  that  is  tight  only  on  one  end; 
and  poorly  fitted  wheels  and  shafts  may  be  made  to  run  rea- 
sonably true  by  using  care  in  fitting  the  keys  and  trying 
the  work  on  lathe  centers  as  it  progresses.  If  means  are 
not  at  hand  for  machining  keys,  as  is  often  the  case  on 
repair  work,  a wooden  pattern  is  first  made  and  the  key 
forged  a little  large,  after  which  the  scale  may  be  ground  off 
on  an  emery  wheel  or  grindstone  and  the  key  filed  to  fit. 

74.  Provision  for  Withdrawing  Keys. — Keys  that 
can  be  driven  out  by  putting  a set  in  the  opposite  end  of 
the  key  seat  are  not  pro- 
vided with  heads;  but  if  the 
seat  is  so  located  that  only 
one  end  is  accessible,  that 
end  must  be  provided  with  FlG-  41- 

a head,  as  shown  at  a , Fig.  41,  for  the  purpose  of  withdraw- 
ing the  keys.  A pinch  bar,  or  wedge,  is  used  between  the 
head  a and  the  hub,  to  back  this  key  out. 


C.  S.  III.— 13 


50 


BENCH,  VISE,  AND  FLOOR  WORK.  § 20 


For  convenience  in  fitting,  large  keys  are  sometimes  made 
with  an  extension  head  3 or  4 feet  long,  as  shown  in  Fig.  42. 


Fig.  42. 


While  backing  out  such  a key,  it  should  be  supported  by 
holding  a sledge  under  the  head  at  the  point  a , while  blows 
are  being  struck  against  the  face  b. 

75.  Taper  of  Keys. — When  keys  are  made  with  a 
taper,  the  taper  is  generally  furnished  by  the  drawing  room, 
but  in  some  shops  the  workman  is  left  to  determine  this  for 
himself;  in  common  practice,  T*¥  inch  to  i inch  per  foot  is 
found  sufficient. 

76.  Round  Keys. — Sometimes  a cylindrical  or  tapered 
pin  is  used  as  a key.  In  this  case  a hole  is  drilled  one-half 
in  the  shaft  and  one-half  in  the  hub ; and  if  the  key  is  to  be 
tapered,  the  hole  is  reamed  to  the  proper  taper.  A key  is 
then  turned  up  to  fit  the  hole,  and  fitted  by  filing  in  the 
lathe,  after  which  it  is  driven  home.  For  very  small  work 
where  there  is  not  much  strain  on  the  parts,  this  style  of 
key  may  do  very  well.  It  is  used  very  generally  to  fasten 
the  hand  wheels  of  globe  valves  to  the  stems.  For  large 
work,  and  especially  where  there  is  not  a good  fit  between 
the  hub  and  the  shaft,  such  a key  should  never  be  used,  as  it 
has  a tendency  to  burst  the  hub. 

77.  Woodruff  Keys. — These  keys  are  made  by  cutting 
a disk  from  a piece  of  cold-rolled  stock,  and  then  splitting  it 

into  two  pieces  along  its 
diameter.  The  keys  thus 
formed  are  of  the  form 
shown  in  Fig.  43.  The 
key  seat  in  the  shaft  is 
made  by  sinking,  a milling 
cutter,  of  a diameter  corresponding  to  the  curve  on  the  key, 


Fig.  43. 


§ 20  BENCH,  VISE,  AND  FLOOR  WORK. 


51 


into  the  shaft  to  such  a depth  that  the  proper  amount  of  the 
key  will  be  left  out  of  the  shaft.  The  key  is  driven  into 
the  shaft,  and  the  wheel,  which  has  previously  been  key- 
seated  with  a seat  whose  depth  is  one-half  its  width,  is 
driven  lightly  on  the  shaft,  and,  if  the  work  has  been  cor- 
rectly done,  the  key  has  only  to  be  slightly  filed  to  let  the 
wheel  into  its  place.  This  key  bears  sidewise,  and  should 
just  fill  the  top  and  bottom.  It  is  a short  key,  and  when  a 
greater  length  is  required  two  or  more  are  put  in  line. 


BENCH,  VISE,  AND  FLOOR  WORK. 

(PART  2.) 


BENCH  WORK  AND  LAYING  OUT. 


TOOLS  AND  FIXTURES  EMPLOYED. 


SCRAPERS. 

1.  Use  of  Scrapers. — Scrapers  are  used  in  machine 
construction  to  fit  or  correct  flat  bearing  surfaces  to  each 
other  and  to  make  flat  or  curved  surfaces  true.  These  sur- 
faces when  flat  are  first  planed,  or  in  some  cases  milled,  as 
true  as  possible ; but  owing  to  the  unequal  hardness  or  tex- 
ture of  the  material,  the  possible  springing  of  the  work  when 
clamped  on  the  planer  or  milling-machine  table,  and  the 
slight  wear  of  the  finishing  tool,  they  are  never  perfect  as 
they  leave  the  machine.  Errors  in  planed  surfaces  such  as 
the  fitter  is  called  on  to  correct  by  scraping  are  caused  in 
several  ways,  the  most  common  of  which  are  wind,  caused 
by  not  having  the  casting  or  piece  firmly  bedded  on  the 
table ; out  of  square,  caused  by  using  try-squares  that  are 
not  true;  angles  that  do  not  match,  caused  by  carelessness 
in  setting  the  head  to  the  angle;  and  by  sand  holes,  spots  of 
scale,  and  hard  spots,  that  the  tool  always  jumps  or  slides 
over.  The  errors  in  planed  work  should  not  exceed  one  or 
two  thicknesses  of  tissue  paper,  and  if  found  to  be  greater, 

§ 21 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


the  work  should  be  sent  back  to  the  planer,  unless  it  is 
found  that  the  errors  are  due  to  hard  spots. 

2.  Forms  of  Scrapers. — The  scrapers  used  on  flat  and 
angular  work  are  the  flat,  the  hook,  the  right-hand  hook, 
and  the  left-hand  hook;  and  for  curved  work,  the  half-round 
and  half-round  end  are  much  used.  For  removing  burrs 
and  scraping  corners  and  countersunk  surfaces,  the  three- 
cornered  scraper  is  generally  used.  The  flat  scraper  is  the 
one  most  used,  as  it  is  the  easiest  to  make,  sharpen,  and 
use,  and  in  expert  hands  it  will  remove  an  astonishing 
amount  of  surface  in  a short  time  with  little  effort. 

Scrapers  are  often  made  of  old  files,  but  they  do  not  work 
well,  because  files  are  made  of  a grade  of  steel,  called  file 
steel , that  can  be  properly  hardened  only  by  the  special 
processes  used  by  the  file  manufacturers.  The  half-round 
and  three-cornered  scrapers  may  be  made  from  any  good 
smooth  or  dead-smooth  files  that  have  become  too  dull  to  use, 
by  simply  grinding  off  the  teeth,  thus  avoiding  the  necessity 
of  rehardening. 

3.  Three-Cornered  Scraper. — The  three-cornered 
scraper  may  be  made  of  a worn-out  file  of  any  good  make. 
The  file  should  have  all  the  teeth  ground  off  and  the  end 
sharpened  at  an  angle  of  about  60  degrees.  It  is  best  to  do 


Fig.  1. 


the  work  on  a wet  grindstone,  for  if  done  on  an  emery  wheel 
and  overheated,  the  scraper  will  be  spoiled.  The  appearance 
of  the  finished  three-cornered  scraper  is  shown  in  Fig.  1. 
In  some  cases  the  edges  from  a to  b are  slightly  curved. 

4.  Flat  Scraper. — The  flat  scraper,  Fig.  2 (a)  and  ($), 
should  be  made  of  any  one  of  the  best  grades  of  tool  steel, 
such  as  Jessop’s,  or  of  the  special  scraper  steel  furnished  by 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


3 


several  American  makers.  It  should  be  made  of  stock  about 
inch  thick  by  1 inch  wide,  with  a tang,  similar  to  that  on 
a file,  which  is  driven  into  a wooden  handle.  The  cutting 
edge  should  be  drawn  to  about  inch  thick  by  If  to 
If  inches  wide,  and  hardened  to  the  greatest  possible  degree. 


(b) 

Fig  2. 

The  sides  should  be  ground  flat,  and  the  end  may  be  slightly 
rounded.  The  end  should  be  ground  by  moving  it  back  and 
forth  along  the  tool  rest,  parallel  to  the  face  of  the  grind- 
stone, thus  making  two  equal  cutting  edges,  as  is  shown 
exaggerated  in  Fig.  3,  which  shows  the 
end  of  the  scraper  as  it  leaves  the  grind-  c 
stone.  The  surfaces  a and  b are  next 
rubbed  on  a good  oilstone,  after  which 
the  tool  is  held  in  a vertical  position  so  d 
that  both  of  the  points  c and  d will  rest 
on  the  stone,  in  which  position  it  is  FlG*  3- 

rubbed  back  and  forth,  grinding  it  into  the  shape  shown  by 
the  dotted  line  ef.  This  makes  the  thin  end  of  the  scraper 
practically  flat.  It  is  now  ready  for  use  and  has  an  equally 
good  cutting  edge  on  each  side. 

5.  Bent,  or  Hook,  Scraper. — The  bent,  or  hook, 
scraper  is  made  in  the  form  shown  in  Fig.  4 ( a ).  It  should 
be  made  with  the  same  care  as  the  flat  scraper,  and  should 
be  ground  to  the  angles  denoted  by  the  lines  af  and  c d, 
Fig.  4 ( b ),  The  cutting  end  is  made  of  the  form  shown 
at  Fig.  4 ( c ).  The  cutting  is  done  with  the  edge  e.  The 
face  bh  is  ground  to  any  convenient  angle  so  as  to  reduce 


4 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


the  area  of  the  surface  be,  which  must  be  finished  on  an 
oilstone.  For  fitting  angular  surfaces  that  cannot  be 


reached  conveniently  by  the  straight  and  regular  hook 
scrapers,  the  right-hand  and  left-hand  hook  scrapers  are 
made,  as  shown  in  Fig.  4 (d)  and  (e). 

6.  Holding  the  Scraper. — The  manner  of  holding 
the  flat  scraper  is  shown  in  Fig.  5.  The  handle  is  held  in 


the  right  hand,  with  the  thumb  extended  along  the  top,  in 
order  to  keep  the  muscles  of  the  hand  and  arm  in  line,  the 


§21  BENCH,  VISE,  AND  FLOOR  WORK. 


5 


same  as  in  filing,  thus  preventing  cramping  the  hand  and 
tiring  the  arm.  The  left  hand  is  applied  as  near  the  cutting 
edge  as  is  convenient,  and  only  enough  pressure  applied  as 
is  necessary  to  remove  the  required  amount  of  metal.  The 
cutting  is  done  by  pushing  the  scraper  away  from  the  oper- 
ator, except  where  it  is  used  for  frosting,  flowering,  or 
finishing,  when  a long  handle  may  be  substituted  and  rested 
on  the  shoulder,  while  both  hands  are  used  to  pull  the  tool 
toward  the  operator.  The  hook  scrapers  are  held  in  much 
the  same  way  as  the  flat  scrapers,  but  are  pulled  toward  the 
workman. 

7.  Proper  Angle  for  Holding  the  Scraper. — The 

flat  scraper  is  usually  held  at  an  angle  of  about  30  degrees 
to  the  surface  of  the  work,  but  this  angle  may  vary  with  the 
material  scraped  and  the  condition  of  the  cutting  edges. 
No  definite  angle  can  be  given  for  other  types  of  scrapers; 
it  must  be  determined  by  trial  with  each  scraper  and  each 
class  of  work. 


SCRAPING  A PLANE  SURFACE. 

8.  Preparation  of  Surface. — A newly  planed  sur- 
face is  scraped  in  the  following  manner:  The  piece  is  placed 
on  any  support  that  will  bring  it  up  to  a convenient  height 
for  the  workman,  who  first  brushes  off  any  dust  or  dirt  that 
may  be  on  the  surface.  He  next  runs  a smooth  or  dead- 
smooth  file  over  the  surface,  to  remove  any  burrs  or  fuzz 
that  may  be  on  it,  and  he  also  touches  off  any  marks  that 
would  indicate  that  a sand  hole  or  hard  spot  had  left  a high 
spot  or  spots. 

9.  Applying  the  Surface  Plate. — A surface  plate, 
prepared  by  thoroughly  cleaning  and  then  coating  with 
marking  material , is  now  placed  face  down  on  the  work  and 
rubbed  back  and  forth  a few  times  over  the  entire  surface. 
No  pressure  is  necessary,  the  weight  of  the  plate  being  suffi- 
cient. When  the  plate  is  removed,  irregular  patches  of 
the  marking  material  will  be  found  on  the  work.  These 
places  indicate  high  spots  in  the  surface,  and  they  are 


6 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


removed  with  a few  strokes  of  the  scraper.  The  workman 
now  wipes  his  hand  clean  of  grit  and  rubs  it  over  the  entire 
face  of  the  surface  plate,  to  smooth  the  marking,  and  then 
rubs  the  plate  over  the  work  again.  More  bearing  spots 
will  be  shown- this  time,  which  are  removed  with  the  scraper. 
The  work  proceeds  in  this  manner  until  the  entire  surface 
of  the  work  is  covered  with  bearing  marks,  when  it  may  be 
called  true. 

The  marking  material,  in  addition  to  showing  the  high 
spots  on  the  work,  acts  as  a lubricant  and  prevents  undue 
wear  on  the  plate  and  the  cutting  or  scoring  of  both  work 
and  plate.  The  more  true  the  surface  operated  on  becomes, 
the  thinner  should  be  the  coating  of  marking  on  the  plate. 
For  some  purposes  the  marking  does  not  afford  sufficient 
lubrication,  and  additional  oil  would  prove  detrimental  to 
the  work.  This  difficulty  may  be  prevented  by  using  a 
plentiful  supply  of  turpentine  on  the  surfaces  while  they 
are  being  rubbed  together.  In  addition  to  lubricating  the 
surfaces,  it  also  facilitates  the  work  of  scraping. 

lO.  Marking  Mixtures. — These  may  consist  of  red 
lead  or  Venetian  red  in  lard  or  machine  oil  or  any  similar 
materials,  red  or  black,  that  are  not  gritty.  In  some  cases, 
special  mixtures  are  furnished  by  the  shop  management  and 
their  use  insisted  on.  The  marking  is  rubbed  with  the 
hand  into  a thin  coating  as  evenly  as  possible  over  the 
plate,  which  is  now  ready  for  use.  It  is  well  to  keep 
the  marking  mixture  in  a tin  box  provided  with  a cover,  so 
that  it  can  be  kept  clean  and  free  from  grit.  Venetian  red 
is  better  than  red  lead,  on  account  of  the  fact  that  it  is  much 
finer  in  texture. 


DRILLS  AND  DRILLING. 

11.  Drilling  Ratchets.  — Ratchet  drilling  is  the 
slowest  method  of  drilling  holes,  and  should  not  be  resorted 
to  if  the  work  can  be  done  by  any  of  the  machine  processes, 
such  as  the  drill  press,  portable  drills,  and  pneumatic  drill- 
ing machine;  but  there  are  places  where  none  of  these  can 


7 


21  BENCH,  VISE,  AND  FLOOR  WORK. 


be  used  or  are  available  and  in  which  cases  the  ratchet  must 
be  used. 

Ratchets  are  generally  made  single  acting;  that  is,  the 
drill  only  cuts  during  the  forward  stroke  of  the  handle;  but 
some  of  the  improved  ratchets  are  made  to  give  a forward 
rotary  motion  to  the  drill  or  cutter  during  both  strokes. 
Ratchets  are  made  to  use  both  square-  and  taper-shank  drills. 

The  taper-shank  twist  drill  is  the  better  tool,  but  it  often 
happens  that  odd  sizes  are  needed  by  men  out  on  repair 
work,  where  it  is  impossible  to  get  the  proper  size  of  twist 
drill,  and  a square-shank  flat  drill  can  be  made  by  any 
blacksmith  or  by  the  man  himself,  or  a flat  drill  already  on 
hand  may  be  made  into  the  required  size  in  a few  minutes, 
either  by  grinding  or  dressing. 

1 2.  Use  of  Drilling  Ratchet. — The  ratchet  is  used 
for  drilling  in  the  following  manner : The  hole  to  be  drilled 


is  laid  out  in  the  usual  way  and  center  punched.  ' Means 
must  be  provided  to  force  the  drill  into  the  material,  which 


8 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


is  usually  done  by  providing  some  sort  of  brace,  or,  as  it  is 
commonly  called  in  the  shop,  an  old  man,  or  a drilling  crow, 
that  will  serve  to  support  the  ratchet  and  drill  in  the  correct 
position  and  at  the  same  time  allow  the  drill  to  be  forced 
into  the  work  by  the  feed-screw. 

The  brace,  drilling  crow,  or  old  man,  is  made  in  a great 
variety  of  ways,  from  a piece  of  flat  iron  or  steel  bent  to  the 
proper  form  to  the  well-designed  adjustable  one  shown  in 
Fig.  6.  This  consists  of  a base  a having  an  upright  b 
carrying  an  adjustable  arm  c that  is  held  by  the  binding 
screw  d. 

The  base  is  made  fast  to  the  work  e by  means  of  a bolt  f 
or  clamp  j,  as  shown.  The  arm  c , which  has  a number  of 
center  holes  in  its  lower  face,  is  set  to  such  a height  that 
the  ratchet  i and  drill  g will  go  under  it.  The  drill  is  set 
square  with  the  work,  or  it  may  be  set  to  lean  slightly 
away  from  the  upright,  as  the  pressure  upwards  on  the 
arm  c will  spring  the  upright  b back  and  so  draw  the  drill 
about  perpendicular.  The  drill  is  rotated  by  means  of  the 
handle  h and  is  fed  into  the  work  by  means  of  the  sleeve  R. 

13.  Special  Ratchets. — Ratchets  for  repair  work  and 
for  use  in  contracted  spaces  are  often  made  very  short,  and 
have  square  holes  in  their  spindles,  so  as  to  use  very  short 
square-shank  drills.  They  are  also  used  in  erecting  machin- 
ery to  ream  holes  in  line. 

14.  Crank- Driven  Portable  Drill. — The  crank-drill 
is  a better  tool  than  the  ratchet,  where  there  is  room 
enough  to  use  it.  This  form  of  drilling  machine  is  clamped 
to  the  work  and  is  operated  by  a crank  that  gives  a continu- 
ous motion  to  the  drill.  The  feed  is  operated  either  auto- 
matically or  by  one  hand,  and  the  crank  is  turned  by  the 
other.  These  drilling  machines  will  work  at  any  angle  and 
form  a very  useful  tool  for  heavy  work. 

15.  Scotch  Drill. — The  Scotch  drill  is  a drilling 
device  formed  very  much  like  an  ordinary  carpenter’s 
brace.  It  is  usually  made  by  bending  a piece  of  steel  or 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


9 


iron  so  that  it  will  form  the  necessary  crank,  providing  one 
end  of  it  with  a suitable  socket  for  the  drill,  which  may  be 
either  square-  or  taper-shanked.  The  other  end  is  provided 
with  a pointed  center  that  may  be  fed  out  by  means  of  a 
screw,  thus  giving  the  feed  to  the  drill.  The  crank  is  rotated 
like  an  ordinary  carpenter’s  brace,  the  device  being  held  in 
place  by  a knee  or  other  suitable  clamping  device.  Some- 
times the  Scotch  drill  is  made  with  two  cranks  arranged 
like  a ship  auger,  so  that  both  hands  may  be  used  at  the 
same  time,  but  usually  only  one  hand  is  employed,  as  the 
other  is  required  to  operate  the  feed-nut. 

16.  Breast  Drill. — The  breast  drill  is  so  named  from 
the  fact  that  it  is  provided  with  a suitable  guard  that  may 
be  placed  against  the  breast  while  drilling,  the  feed  being 
obtained  by  a pressure  brought  to  bear  on  the  drill  by  the 
body.  The  drill  is  usually  operated  through  bevel  gears  by 
a crank  on  the  side  of  the  machine.  This  style  of  drill  is 
very  largely  used  for  drilling  small  holes  for  attaching  name 
plates,  and  for  similar  light  work. 


BROACHES  A\I)  BROACHING. 

1 7.  Broaching. — Broaching,  or  drifting,  is  the 

process  of  forming  holes  by  forcing  a cutter  of  the  exact 
form  required  through  holes  previously  drilled.  In  all 
broaching  operations,  the  greatest  amount  of  stock  possible 
must  be  removed  by  drilling,  and  if  much  remains  for  the 
broaching  tools,  they  should  be  so  designed  that  each  tool 
will  be  given  an  equal  amount  of  material  to  take  out. 

18.  Simple  Square  Broach. — The  form  of  broach 
depends  largely  on  the  nature  and  quantity  of  the  work  to 
be  done.  If  this  is  only  a small  amount,  the  broach  must  be 
as  inexpensive  as  possible.  In  this  case,  most  of  the  work  is 
thrown  on  the  drills  or  other  means  used  for  roughing  out 
the  hole,  and  the  broach  depended  on  only  for  finishing  the 
hole. 


10 


BENCH,  VIvSE,  AND  FLOOR  WORK. 


§21 


The  simplest  form  of  broaching  is  illustrated  in  making  a 
socket  to  fit  a £-inch  square  in  a tap  socket  or  a chuck-screw 
wrench.  The  square  may  be  laid  out  on 
the  end  of  a piece  of  round  stock,  as  in 
Fig.  7.  A ^-inch  circle  a is  first  drawn 
from  the  center  mark  b,  and  the  square  c is 
laid  off.  Four  ^-inch  holes  d are  now  drilled 
^ inch  deeper  than  the  hole  is  to  be  and  just 
touching  the  lines  of  the  square.  The^-inch 
hole  is  next  drilled,  which  leaves  the  hole  as  shown  in 
Fig.  8 (a).  A square  piece  of  steel  having  the  proper 
temper  may  now  be  driven  easily  to  the 
bottom  of  the  hole.  Fig.  8 (b)  shows 
this  form  of  broach;  it  tapers  a little 
from  the  cutting  edge  e to  f. 

1 9.  Use  of  Several  Broaches  in 
a Set. — In  cases  where  there  is  a con- 


(a) 

f 


(*) 


Fig.  8. 

siderable  amount  of  any  given  class  of  work  to  be  done,  it  is 
best  to  use  several  broaches  following  one  another,  each 
removing  a portion  of  the  stock.  In  the  case  illustrated  in 
Figs.  7 and  8,  the  greater  part  of  the  metal  at  the  corners 
was  removed  by  drilling  small  holes,  and  in  some  cases  some 
additional  metal  was  chipped  out.  If  there  is  much  of  this 
work  to  be  done,  all  the  metal  in  the  corners  may  be 
removed  by  passing  a series  of  broaches  through  the  work. 
In  Fig.  9,  the  forms  of  four  broaches  for  squaring  a Linch 
round  hole  that  extends  through  the  piece  are  shown  at 
e,  f,  g,  and  h.  All  the  broaches  should  be  provided  with 
several  cutting  edges,  as  shown  between  b and  c , and  a 


21 


BENCH,  VISE,  AND  FLOOR  WORK. 


11 


guide  pin,  as  shown  at  a b,  in  the  upper  part  of  Fig.  9, 
which  represents  the  finishing  broach. 

20.  Making  a Set  of  Broaches. — The  pieces  of  steel 
to  form  the  set  are  first  centered  and  milled  to  the  size  of 
the  square,  after  which  the  guide  from  a to  b is  turned  to 
the  size  of  the  largest  hole  that  can  be  drilled  inside  the 
square,  which  in  this  case  is  \ inch.  The  toothed  part  from 


Fig.  9. 


b to  c is  cut  either  by  milling  or  planing,  or  the  teeth  may 
be  cut  in  the  lathe  and  afterwards  backed  off  for  clearance 
by  hand.  The  size  from  c to  d should  be  made  slightly 
smaller  than  the  toothed  part,  so  that  it  will  easily  pass 
through  the  hole. 

The  various  broaches  of  the  set  are  made  of  such  form 
that  each  takes  out  nearly  an  equal  amount  of  stock.  The 
broach  marked  e is  driven  through  first,  and  is  followed  in 
succession  by  fy  g,  and  //,  which  finishes  the  hole  to  size. 

21.  Grinding  the  Teeth. — In  a new  broach,  the 
teeth  from  b to  c are  all  of  the  same  size,  so  that  only  the 
leading  teeth  cut  and  those  behind  simply  steady  the  broach. 
As  the  front  teeth  become  dull,  they  are  ground  on  . the 
front  or  flat  face,  and  thus  are  reduced  in  size,  so  that  the 
other  teeth  farther  back  must  be  depended  on  to  do 
the  finishing. 

In  preparing  the  blanks  for  the  broaches  shown,  the 
corners  in  the  broaches  *?,  f,  and  g can  be  turned  off  in  the 
lathe,  and  if  desired  both  the  cylindrical  and  the  flat  surfaces 


12 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


can  be  finished  by  grinding  after  hardening.  The  broaches 
described  are  intended  to  be  driven  by  a hammer,  but  they 
may  be  forced  through  by  a power  or  hydraulic  press. 

ZZ.  Broaching  Keyways.  — Keyways  may  be 
broached  more  quickly  and  accurately  than  they  can  be 
chipped  by  hand.  In  some  cases,  quite  large  and  long 
keyways  are  formed  in  this  way,  the  broaches  being  driven 
by  means  of  sledges. 

The  necessary  tools  for  broaching  keyways  are  shown  in 
Fig.  10.  First  there  must  be  a plug,  Fig.  10  (a),  turned  to 
the  proper  diameter  cd  so  that  it  just  fits  the  bore  of  the 
hub,  and  it  must  be  of  sufficient  length  to  pass  entirely 


through  the  hub.  The  plug  is  provided  with  a collar  e , which 
prevents  it  from  passing  too  far  into  the  hub.  A slot  or 
key  way  having  the  same  taper  as  the  required  keyway  in  the 
hub  is  cut  in  the  plug,  as  indicated  by  the  dotted  line  a b. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


13 


The  cutting  in  the  hub  is  done  by  the  tool  shown  in 
Fig.  10  ( c ).  The  cutting  edge  is  at  j,  and  the  thickness^/ 
must  be  equal  to  the  depth  of  the  narrow  end  of  the  slot  b d. 
In  order  to  make  the  broach  cut,  liners  are  placed  in  the 
groove  behind  the  broach;  one  of  these  liners  is  shown  at 
Fig.  10  ( b ).  The  liners  are  made  of  sheet  metal,  and,  if  the 
keyway  is  a large  one,  after  several  thin  liners  are  in  place 
they  may  be  removed  and  replaced  by  one  thick  one,  after 
which  the  thin  ones  may  be  replaced  one  by  one,  as  the  suc- 
cessive cuts  are  taken.  This  method  of  employing  some 
thick  liners  reduces  the  number  of  joints  that  can  be  com- 
pressed as  the  broach  is  being  driven,  and  so  makes  the  work 
more  uniform. 

The  broach  is  provided  with  a guide  gi,  which  enters  the 
hole  first,  and  the  portion  g h must  be  at  least  equal  in  length 
to  the  slot  a b , so  that  the  broach  can  be  driven  clear  through. 
The  face  j k of  the  broach  should  be  perpendicular  to  the 
face  to  be  cut.  The  broach,  if  very  large,  may  be  made  of 
machine  steel  and  provided  with  an  inserted  blade  or  cutter 
at  j.  The  cutting  edge  of  a broach  should  be  hardened  to 
a brown  or  dark  straw  color. 

23.  Machine  Broaching. — Broaches  for  large  holes, 
or  for  large  numbers  of  similar  holes,  such  as  are  met  with 
in  manufacturing,  are  forced  through  the  work  by  power- 
driven  machines  or  hydraulic  presses  that  support  the  work 


and  also  guide  the  tool.  Broaches  used  in  these  machines 
are  designed  with  special  reference  to  the  form  of  the  hole 
and  the  quantity  of  stock  to  be  removed,  and  a dozen 
broaches  may  be  made  to  work  out  a single  form  of  hole, 
each  one  taking  a light  cut. 


C.  6-.  III.— 14 


14 


BENCH  VISE,  AND  FLOOR  WORK. 


21 


Broaches  for  the  machine  work  may  be  made,  as  shown  in 
Fig.  11,  with  a countersunk  center  in  the  head  and  a cor- 
responding external  center  on  the  point.  The  No.  1,  or 
smaller,  broach  of  a set  is  forced  downwards  as  far  as  it  will 
go,  and  then  the  No.  2 is  placed  on  it,  with  its  point  in  the 
reamed  center  to  guide  it;  this  one,  also,  is  forced  down- 
wards, driving  the  first  one  through.  This  is  repeated  until 
all  the  broaches  have  been  driven  through  the  hole.  In 
some  cases,  a single  broach  is  forced  through  by  hydraulic 


pressure  and  made  to  finish  a hole  in  one  operation.  Fig.  12 
shows  a broach  and  broached  piece.  The  broach  in  this 
case  has  rounded  corners,  which  illustrates  a practice  that 
should  be  followed  wherever  practicable,  as  teeth  of  this  form 
are  much  less  liable  to  break  than  those  of  square-cornered 
broaches.  The  notches  a allow  the  broach  to  be  started 
without  taking  the  whole  cut,  and  when  it  has  entered  far 
enough  to  have  sufficient  support  to  steady  it,  the  whole 
teeth  b commence  cutting  and  finish  the  work. 

24.  Angle  of  Broach.  Teeth. — The  teeth  on  broaches 
are  sometimes  cut  diagonally  across  the  sides,  but  these  do 
not  cut  as  easily  as  those  cut  square  across,  and  they  also 
have  a tendency  to  force  the  ‘broach  to  one  side  or  to  make 
it  take  a spiral  course,  thus  causing  some  of  the  teeth  to  run 
into  the  stock  and  make  a rough  hole.  For  this  reason,  the 
teeth  are  generally  made  straight  across. 

25.  Lubrication  of  Broaches. — For  cutting  most 
metals,  broaches  require  an  abundant  supply  of  lard  oil.  In 
broaching  keyways  in  cast  iron,  oil  is  not  required  so  much 
for  the  cutting  operation,  but  the  back  and  sides  of  the 
broach  should  be  well  lubricated. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


15 


REAMERS  AND  REAMING. 

26.  Object  of  Hand  Reaming. — The  continued  use 
of  machine  reamers  dulls  their  cutting  edges  and  at  the 
same  time  slightly  reduces  their  diameters.  For  some  work, 
a hole  yoVo-  inch  under  size,  such  as  would  be  produced  by  a 
worn  reamer,  would  not  be  objectionable,  but  in  addition  to 
being  small,  the  hole  will  be  comparatively  rough.  These 
defects  may  be  overcome  by  hand-reaming  the  hole. 

27.  Ordinary  Hand  Reamer. — The  hand  reamer 
shown  in  Fig.  13  illustrates  one  form  of  this  class  of  tools. 
The  body  a is  finished  to  the  correct  standard  size,  and  the 
shank  is  made  of  such  size  that  it  will  act  as  a guide  when 


Fig.  13. 

the  hole  to  be  reamed  is  longer  than  the  fluted  part  a.  A 
groove  c,  turned  about  one  diameter  from  the  lower  end, 
serves  as  a stopping  place  for  the  wheel  while  grinding,  and 
below  this  the  diameter  is  about  yqVo  inch  smaller  than  at  a. 
From  the  point  c to  d,  about  one  diameter,  the  reamer  is 
tapered  up  to  the  full  size,  and  from  d up  it  is  parallel.  The 
hand  reamer  is  used,  as  its  name  implies,  only  by  hand. 
The  end  e is  entered  into  the  hole  left  small  by  the  under- 
sized machine  reamer  and  acts  as  a guide,  and  the  taper 
from  c to  d removes  the  stock,  while  the  parallel  part  a 
maintains  the  size.  The  small  amount  removed  insures  the 
durability  of  the  tool  and  the  smoothness  of  the  hole.  For 
cast  iron  and  brass,  the  reamer  should  be  entered  and  twisted 
through  the  hole,  using  enough  pressure  to  force  it  through 
quickly.  In  the  case  of  cast  iron,  the  use  of  oil  will  give  a 
smoother  hole  than  can  otherwise  be  obtained.  For  wrought 
iron  and  steel,  it  should  be  well  lubricated  with  lard  oil. 

28.  Step  Reamer.— The  reaming  of  taper  holes,  par- 
ticularly large  ones,  in  tough  and  hard  metals,  is  greatly 


16 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


facilitated  by  using  the  step  reamer  illustrated  in  Fig.  14. 
The  small  end  a of  this  reamer  is  made  the  size  of  the  small 
end  of  the  hole.  A hole  of  a size  corresponding  to  a is 
drilled  into  or  through  the  work  as  required.  The  step 
reamer  is  then  started  in  and  run  to  the  -necessary  depth. 
This  reamer  cuts  only  on  the  end  of  each  step,  as  at  b,  c , etc., 
the  diameter  of  the  reamer  being  slightly  less  at  the  top  of 
each  step  than  at  the  lower  end;  for  instance,  the  diameter 
is  smaller  at  e than  it  is  at  d , in  order  that  the  tool  may  not 
bind  in  the  hole.  Clearance  is  also  given  the  cutting  edge 


Fig.  14. 

from /to  g.  This  reamer  is  cut  with  four  flutes,  and  there- 
fore has  four  sets  of  cutting  edges.  The  half-round  notches  h 
are  cut  to  make  a stopping  place  for  the  wheel  while  grind- 
ing. The  use  of  this  reamer  does  away  with  the  necessity 
of  using  a number  of  different-sized  drills  to  prepare  the  hole 
for  reaming.  After  the  step  reamer  has  removed  the  stock, 
a notched  taper  reamer  is  run  in  to  remove  the  steps,  and 
after  that  the  finishing  reamer  smooths  the  hole.  Step  and 
taper  reamers  intended  for  use  in  the  lathe  or  by  hand  are 
provided  with  square  shanks,  but  when  made  for  use  in 
drilling  or  boring  machines  they  must  be  provided  with 
taper  shanks,  so  as  to  fit  the  sockets. 

29.  Taper  Reaming. — Taper  holes  are  frequently 
hand-reamed,  to  make  them  of  the  correct  size  and  smooth- 
ness. This  is  done  after  the  stock  is  removed  by  the  rough- 
ing and  finishing  reamers.  The  taper  hand  reamer,  when 
not  in  use,  should  be  kept  in  a box  or  tied  up  in  a heavy 
paper  covering,  as  any  nick  or  dent  on  its  cutting  edges  will 
seriously  mar  the  hole.  The  taper  hand  reamer  must  be 
used  with  great  care.  It  should  be  carefully  placed  in  the 
hole,  well  oiled  if  in  wrought  iron  or  steel,  and  turned  with 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


17 


enough  pressure  to  insure  its  cutting  from  the  very  first;  for 
turning  a taper  hand  reamer  in  a hole  when  it  does  not  cut 
will  soon  ruin  it. 

Valve  bushings,  which  must  be  perfectly  smooth  and 
parallel  internally,  are  often  reamed  with  undersized  machine 
reamers  and  then  forced  into  place,  after  which  a hand 
reamer  is  run  through  them  to  correct  their  defects. 

30.  Advantage  of  Vertical  Reaming. — All  ream- 
ing, whether  hand  or  machine,  is  better  if  done  in  a vertical 
position.  This  is  so  because  the  weight  of  the  reamer,  if 
working  horizontally,  tends  to  ream  downwards,  and  so 


either  carries  the  reamer  out  of  line  or  tends  to  take  more 
out  of  the  bottom  side  of  the  hole.  Also,  any  chips  or 
cuttings  will  fall  out  of  the  vertical  hole,  but  in  the  hori- 
zontal hole  they  remain  between  the  teeth  of  the  reamer  and 
often  scratch  or  score  the  work. 


18 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


31.  Example  of  Vertical  Reaming. — Fig.  15  shows 
the  practice  of  a prominent  engine  builder.  The  pulleys 
for  these  engines  are  first  put  on  the  boring  mill  and  turned 
to  inch  over  the  finished  size;  the  hole  is  bored  about 

inch  small  and  then  hand-reamed  to  size,  after  which  the 
wheel  is  put  on  a mandrel  and  the  face  turned  true  and  to 
size.  The  reaming  is  done  in  the  following  manner:  The 
wheel  is  placed  on  blocks,  as  shown,  and  the  reamer’s  shank  b 
is  passed  up  through  the  bore  and  hooked  to  the  threaded 
rod  d.  A split  bush  c is  placed  around  the  shank  b and 
pushed  down  into  the  bore  to  act  as  a guide.  A double-end 
wrench  is  placed  on  the  square  of  the  shank  at  e , and  two 
men  walk  around  the  wheel  to  turn  the  reamer.  The 
threaded  rod  d passes  through  a nut,  not  shown  in  the  cut, 
and  this  feeds  the  reamer  a upwards  through  the  hole.  The 
reamer  a is  shown  just  as  it  leaves  the  finished  hole.  Another 
finishing  reamer  is  shown  at  f. 

32.  Reaming  Holes  in  Line. — Holes  may  be  reamed 
in  line  in  the  following  manner:  The  holes'  in  two  or  more 
castings  that  are  to  be  bolted  together  are  first  laid  out  as 
close  as  possible  to  their  correct  location  ; all  those  in  one 
piece  are  drilled  and  reamed  to  size,  and  the  corresponding 
holes  in  the  next  piece  are  drilled  about  ^ inch  smaller;  then 
the  two  castings  are  clamped  together  in  their  correct  posi- 
tion, and  a reamer  the  same  size  as  the  finished  hole,  which 
will  cut  only  on  its  end,  is  put  through  the  reamed  part  of 
the  hole  and  ratcheted  through  the  smaller  hole,  thus  bring- 
ing them  perfectly  in  line.  This  work  must  often  be  done 
in  very  contracted  or  limited  spaces,  and  for  such  work, 
special  reamers,  called  rose  bits  or  rose  reamers,  must  be 
made. 


INSIDE  THREAD  CUTTING. 

33.  Methods  of  Tapping.  — Holes  are  threaded  in 
three  ways:  first,  by  cutting  in  the  lathe;  second,  by  using 
a special  tapping  fixture  in  the  drilling  machine;  and  third, 
by  hand.  The  first  two  methods  provide  their  own  means 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


19 


of  keeping  the  tap  square  with  the  work,  but  in  hand  tapping 
much  depends  on  the  skill  of  the  workman. 


34.  Squaring  Tapped  Holes. — Two  sorts  of  hand 
taps  are  in  common  use.  The  first  kind,  Fig.  16  ( a ),  is  made 


(b) 

Fig.  16. 


with  a parallel  end  be  the  size  of  the  bottom  of  the  thread. 
This  parallel  end  fits  the  hole  made  by  the  tap  drill,  so  that 
by  the  exercise  of  a little  care  on  the  part  of  the  user  a 
squarely  tapped  hole  is  the  result. 

The  other  style,  Fig.  16  ( b ),  is  tapered  from  d to  e\  con- 
sequently, it  will  not  stand 
square  with  the  hole.  To  tap 
a hole  square  with  (b),  the  tap 
should  be  well  oiled,  placed  in 
the  hole,  and  given  two  or 
three  turns  with  a double- 
ended  wrench.  At  this  point 
remove  the  wrench  and  apply 
a square  to  the  tap  in  the  man- 
ner shown  at  a , Fig.  17.  Try 
the  square  at  the  next  flute, 
and  if  the  tap  shows  out  of 
square  apply  pressure  enough 
sidewise  on  it  with  the  wrench 
while  turning  to  bring  it 

square  with  the  surface.  • Repeat  these  trials  until  the  tap 
is  found  to  be  square.  If  a square  is  not  at  hand,  a wide 


20 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


6-inch  steel  rule  may  be  used  instead,  as  at  b , Fig.  17.  The 
tap  shown  in  Fig.  16  (a)  will  go  in  reasonably  straight,  but 
the  beginner  will  do  better  work  with  it  by  using  the  same 
precautions  as  with  the  other  style. 

35.  Tapping  Jig. — The  tapping  jig  shown  in  Fig.  18 
is  sometimes  used.  It  consists  of  a piece  of  iron  or  steel 
bent  to  the  form  shown  at  a , Fig.  18  (a).  The  bottom 
surface  be  is  planed  flat,  and  a hole  d the  size  of  the  tap 
shank  is  drilled  square  to  be.  A plug  e is  turned  to  fit  d 
and  the  hole  f to  be  tapped.  To  use  this  tool  or  jig,  put 


the  plug  into  the  hole  d and  then  push  it  into  f,  as  shown ; 
clamp  the  jig  a fast  at  the  point  g,  and  see  that  the  plug  e 
fits  easily  in  both  holes;  remove  the  plug,  and  replace  it  with 
the  tap,  which  will  be  held  in  the  correct  position  to  tap  the 
hole,  as  shown  in  Fig.  18  ( b ).  The  hole  d in  the  jig  may  be 
made  as  large  as  the  largest  tap,  and  a set  of  bushings  made 
to  adjust  it  to  taps  having  smaller  shanks. 

36.  Producing  Smooth  Threads. — It  is  sometimes 
desirable  to  tap  holes  with  particularly  smooth  threads. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


21 


This  may  be  done  by  first  tapping  the  hole  with  a V-thread 
tap  and  then  following  it  with  a tap  having  the  United 
States  standard  form  of  thread.  The  V-tap  thread  will  leave 
enough  material  so  that  the  United  States  standard  thread 
tap  will  perform  the  same  work  in  the  tapped  hole  that  the 
hand  reamer  does  in  the  plain  hole. 

37.  Number  of  Taps  Necessary. — Ordinary  holes 
in  thin  stock  may  be  tapped  in  one  operation  bv  running  the 
taper  tap  clear  through  the  piece;  but  if  the  hole  is  of  great 
depth,  or  of  hard  material,  a second,  or  plug,  tap  must  be 
run  down,  to  relieve  the  long  cut  made  by  the  taper  tap.  By 
using  these  two  taps  alternately,  holes  may  be  tapped  to  any 
depth  that  the  taps  will  reach.  Neither  the  taper  nor  the 
plug  taps  will  thread  a hole  clear  to  the  bottom,  so  when 
this  is  necessary,  a third  tap,  called  a bottoming  tap , is 
screwed  clear  to  the  bottom  of  the  hole.  Care  should  be 
taken  in  using  this  tap,  as  the  end  teeth  are  easily  broken 
by  the  heavy  cut. 

38.  Pipe  Threads. — -The  threads  on  pipe  are  of  the 
V type,  and  to  insure  tight  fits  the  threaded  parts  are  made 
tapering.  The  standard  taper  for  the  threaded  portion  of 
pipe  is  ^ inch  to  the  inch  or  |-  inch  to  the  foot.  The  holes 
to  be  tapped  for  small  sizes  of  pipe  are  usually  drilled  to  the 
size  of  the  bottom  of  the  thread  at  the  small  end  of  the  tap, 
and  then  the  pipe  tap  run  down  to  the  proper  depth ; but 
for  the  large  work,  a reamer  having  the  same  taper  as  the 
tap  is  run  in  to  take  out  some  of  the  stock.  This  reaming 
leaves  the  right  amount  of  stock  for  threading,  and  saves 
unnecessary  wear  on  the  tap. 


WRENCHES. 

39.  Double-End  Wrench. — The  wrenches  used  for 
turning  taps  and  hand  reamers  are  made  in  a great  variety 
of  forms.  Some  are  made  solid,  with  one  or  more  holes  for 


22 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


different-sized  shanks,  but  the  best  wrenches  are  made  of 
the  form  shown  in  Fig.  19.  This  wrench  is  adjustable  to 
several  different  sizes  of  tap  squares.  The  length  of  the 
handles  of  different  wrenches  of  this  type  are  proportionate 
to  the  diameters  of  the  taps  on  which  they  may  be  safely 


fig.  19 


used.  Holes  must  frequently  be  tapped  in  spaces  where 
wrenches  of  this  type  cannot  be  turned,  and  the  single-end 
wrench  must  be  substituted ; but,  where  practicable,  an  exten- 
sion should  be  placed  on  the  tap  and  a double-end  wrench 
used,  as  by  this  means  holes  can  be  tapped  more  nearly  true 
and  the  danger  of  breaking  the  tap  is  reduced  to  a minimum. 

40.  Special  Double  Wrench.  — Special  forms  of 
wrenches  are  sometimes  made  for  special  work.  The  wrench 
shown  in  Fig.  20,  which  is  commonly  used  in  the  boiler 
shop,  and  sometimes  in  the  machine  shop,  may  be  taken  as 
an  illustration  of  this  class,  and  may  suggest  others  that  are 


Fig.  20. 


suitable  for  special  operations.  The  tap  wrench  illustrated 
in  Fig.  20  is  called  a stay  bolt  tap  wrench , and  is  made 
of  -|-inch  round  steel  bent  to  the  form  shown.  The  square 
hole  a is  provided  for  the  special  staybolt  tap  shown.  Two 
handles  c and  d are  formed  by  the  bends,  and  by  using  both 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


23 


hands,  the  tap  may  be  given  a continuous  rotary  motion. 
Whenever  possible,  these  taps  are  screwed  clear  through  and 
taken  out  on  the  other  side,  instead  of  screwing  them  back 
again,  as  is  done  with  the  ordinary  hand  tap. 

41.  Single-End  Wrenches.  — Single-end  wrenches 
are  made  both  open  and  closed ; that  is,  they  are  so 
arranged  that  they  simply  enclose  three  sides  of  a square 
nut,  or  four  sides  of  a hexagonal  nut,  or  are  so  made  that 
they  entirely  surround  the  nut.  The  open-end  wrenches 
have  certain  advantages,  in  that  they  do  not  have  to  be 
slipped  over  the  end  of  the  bolt  or  nut;  they  are  made 
both  with  the  sides  of  the  jaws  parallel  to  the  line  of  the 
handle  and  with  the  sides  of  the  jaws  set  at  an  angle  to  the 
center  line  of  the  handle. 

For  some  purposes  the  straight  wrench  with  the  sides  of 
the  jaws  parallel  to  the  handle,  as  illustrated  in  Fig.  21,  is 
suitable,  but  for  work  in  contracted 
spaces  it  is  best  to  give  a wrench 
intended  for  hexagonal  heads  or 
nuts  an  offset,  as  shown  in  Fig.  22. 

This  offset  should  be  15  degrees. 

The  manner  of  using  the  wrench 
is  illustrated  in  the  four  views  in 
Fig.  22.  In  Fig.  22  (<?),  the  first  hold  is  shown,  the  wrench  a 
being  placed  on  the  nut  f.  In  this  case,  the  wrench  handle  b 
operates  betweeen  the  obstructions  c and  d.  The  wrench  is 
first  placed  as  shown  in  Fig.  22  (a),  and  the  handle  moved 
to  the  left  into  the  position  shown  in  Fig.  22  (b).  The 
wrench  is  then  turned  over  and  placed  on  the  nut,  as  shown 
in  Fig.  22  (c),  when  it  may  be  given  another  movement, 
bringing  it  into  the  position  shown  in  Fig.  22  (d).  This 
will  have  advanced  the  nut  one-sixth  of  a revolution  in  two 
moves,  from  which  it  will  be  seen  that  12  movements  are 
necessary  to  make  a complete  revolution ; as  there  are 
360  degrees  in  the  whole  circle,  it  is  evident  that  the  nut 
is  moved  30  degrees  at  each  stroke  of  the  wrench.  If  the 
wrench  were  made  straight,  as  shown  in  Fig.  21,  it  could  not 


24 


BENCH,  VISE,  AND  FLOOR  WORK. 


21 


be  operated  in  the  manner  illustrated  in  Fig.  22,  but  the  nut 
would  have  to  be  so  located  that  there  would  be  a clear  space 
in  which  the  wrench  could  make  one-sixth  of  a revolution. 


42.  The  open-end  wrench  is  especially  adapted  for 
screwing  on  nuts,  screwing  in  cap  bolts,  etc.,  but  for  oper- 
ating taps,  a closed,  or 
solid-end,  wrench 
similar  to  that  shown  in 
Fig.  23  is  required. 
These  may  be  made 
with  the  sides  of  the 
jaws  parallel  to  the  handle,  as  shown  in  Fig.  21,  or  they 
may  be  made  with  the  sides  offset,  as  shown  in  Fig.  22. 
If  the  wrench  is  intended  for  a square-end  tap,  the  offset 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


25 


should  be  one-half  of  45  degrees,  or  22£  degrees,  as  shown 
in  the  illustration.  This  will  enable  the  operator  to  advance 
the  tap  { of  a revolution,  in  case  there  are  obstructions  so 
placed  that  it  is  impossible  to  make  a greater  fraction  of  a 
turn  than  this. 

-43.  Socket  Wrenches. — The  most  common  form  of 
socket  wrench  is  illustrated  in  Fig.  24  (a).  It  is  used  to 
turn  nuts  and  bolt  heads  set  in 
recesses  below  the  surface  of  the 
work,  as  illustrated  in  Fig.  24  (b). 

These  wrenches  are  made  with 
either  square  or  hexagonal  sockets, 
as  the  work  may  require.  The 
sockets  are  made  by  laying  out 
the  desired  form  on  the  end,  drill- 
ing one  or  more  holes  to  remove 
the  majority  of  the  stock — in  the 
case  of  a large  wrench,  chipping 
out  some  of  the  remainder  of  the 
stock,  and  then  broaching  the 
hole  to  the  desired  form.  Socket  (*>) 

wrenches  may  be  made  with  the  FlG-  24- 

sides  of  the  opening  in  the  end  of  the  wrench  parallel  or 
perpendicular  to  the  handle  b,  Fig.  24  ( a ),  which  will  give 
results  similar  to  that  shown  in  the  open-end  wrench  in 
Fig.  21;  or  they  may  be  made  with  a 15-degree  offset  for 
hexagonal  wrenches,  and  22-J-  degrees  offset  for  square 
wrenches,  as  illustrated  in  Figs.  22  and  23.  The  offset  is 
generally  not  as  important  in  the  socket  wrench  as  in  the 
solid-end  or  open-end  wrench,  on  account  of  the  fact  that 
the  shank  c , Fig.  24  ( a ),  of  the  wrench  is  usually  made  long 
enough  to  clear  all  obstructions. 

44.  Socket  Extensions  for  Wrenches. — When  it 
becomes  necessary  to  tap  holes  in  contracted  spaces,  or  to 
screw  in  studs  or  bolts  in  such  locations,  it  is  sometimes 
possible  to  reach  the  work  by  means  of  a socket  extension 


26 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


similar  to  that  shown  in  Fig.  25.  This  consists  simply  of 
a long  stem  a having  at  one  end  a socket  c}  of  the  form 
required  to  fit  the  work,  and  a square  b on  the 
other  end  intended  to  fit  any  ordinary  double- 
end or  single-end  wrench.  Usually,  these  socket 
extensions  are  used  only  with  double-end 
wrenches. 

45.  Ratchet  Wrenches. — In  the  case  of 
practically  all  single-end  wrenches,  it  is  neces- 
sary to  remove  the  wrench  and  replace  it  on  the 
nut  after  a portion  of  a revolution  has  been 
made.  As  there  are  a great  many  places  where 
nothing  but  a single-end  wrench  can  be  used, 
much  valuable  time  is  lost  in  this  changing 
of  the  wrench.  To  overcome  this  difficulty, 
ratchet  wrenches  have  been  introduced.  A 
good  type  of  adjustable  ratchet  wrench  is  illus- 
trated in  Fig.  26,  in  which  the  jaws  a can  be 
adjusted  by  means  of  the  screws  b so  that  they  will  accom- 
modate a number  of  sizes.  A handle  c can  be  moved  for- 
wards through  whatever  portion  of  a stroke  the  location  will 
permit,  and  then  return  for  another  stroke.  It  is  possible 


Fig.  26. 


to  make  as  small  a fraction  of  a revolution  as  one  tooth  of 
the  ratchet,  shown  at  d.  This  style  of  ratchet  wrench  has 
but  a single  pawl  engaging  the  ratchet,  and  hence  there  is 
bound  to  be  some  lost  motion  before  the  pawl  takes  hold 
of  a tooth  on  the  forward  stroke. 

46.  Teeth  of  Ratchet  Wrench. — It  is  advantageous 
to  have  the  teeth  of  the  ratchet  as  coarse  as  possible,  so  as 
to  give  them  the  requisite  strength;  in  order  to  obtain  the 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


27 


effect  of  fine  teeth,  which  give  the  least  amount  of  lost 
motion,  the  multiple-pawl  ratchet  has  been  introduced. 
This  is  illustrated  in  Fig.  27.  in  which  the  ratchet  a has 
12  teeth;  5 pawls  b are  so  placed  that  only  one  of  them  will 


engage  a tooth  at  a time,  as  shown  at  c.  By  moving  the 
pawls  back  { of  a space  between  th-e  teeth,  the  next  pawl 
will  come  in  contact  as  at  d , and  hence  the  lost  motion  can- 
not be  greater  than  \ of  y1^,  or  ^ of  a revolution. 

47.  Studholt  Wrench. — For  driving  studs  by  means 
of  a ratchet,  a special  stud  holder  is  provided,  as  shown  in 


Fig.  28. 


Fig.  28.  The  stud  a is  screwed  into  the  socket  b , and  then 
the  point  of  the  setscrew  c is  run  down  against  the  end  of 


28 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


the  stud  so  as  to  lock  it  in  the  socket.  The  setscrew  c is 
held  in  place  by  means  of  a locknut  d.  A stud  driver  is 
operated  by  means  of  a ratchet  on  a square  e.  This  style 
of  stud  driver  is  ordinarily  used  in  a very  thin  ratchet,  as 
shown  at  c' . 

Ratchets  may  also  be  applied  to  socket  extension  wrenches 
where  these  must  be  used  in  locations  in  which  a complete 
revolution  cannot  be  made.  The  time  saved  in  putting  the 
studs  into  a single  large  engine  will  usually  more  than  pay 
for  the  price  of  a ratchet  wrench  and  suitable  stud  driver. 


OUTSIDE  THREAD  CUTTING  AND  PIPEWORK. 

48.  Die  Stock  and  Square  Dies. — Outside  threads 
of  various  pitches  and  sizes  must  often  be  cut  by  hand. 
Dies  for  such  work  are  made  to  cut  threads  on  pieces  rang- 
ing from  ^ inch  to  2 inches  in  diameter.  A form  of  stock 
and  die  that  has  many  advantages  is  shown  in  Fig.  29  ( a ). 
The  stock  a has  an  oblong  opening  b provided  with  guides 


for  holding  the  split  die  c,  which  is  closed  by  a setscrew. 
The  form  of  these  dies  is  shown  in  Fig.  29  (b).  They  are 
so  constructed  that  the  cutting  is  done  at  the  points  f, 
which  also  steady  the  dies  when  starting  on  the  work.  Bolts 
can  be  threaded  standard,  undersize,  or  oversize  with  these 
dies.  For  example,  a No.  14  screw,  a ^-inch,  or  a -^-inch 
screw,  all  20  threads  per  inch,  can  be  fitted  with  one  pair 


BENCH,  VISE,  AND  FLOOR  WORK. 


29 


§21 


of  dies.  They  may  be  made  in  any  size  and  should  be 
tapped  with  an  oversize  tap  in  order  to  provide  clearance. 
These  dies  are  especially  adapted  to  repair  work  where  the 
variety  of  work  is  great  and  the  quantity  small.  With  these 
dies  several  cuts  must  be  taken  to  cut  a full  thread.  A pair 
of  blank  dies  with  suitable  notches  cut  in  them,  used  in  this 
stock,  makes  an  excellent  tap  wrench. 

49.  Die  Stock  and  Round  Dies.* — Standard  work  is 
best  done  with  any  of  the  many  forms  of  round  dies,  one  of 
which  is  illustrated  in  Fig.  30  (#),  (£),  and  (^).  When  in  use, 


the  die  is  held  in  a die  stock,  of  the  form  shown  in  Fig.  31. 
The  die  is  made  of  two  parts  a and  b.  Fig.  30  (a)  showing 
the  two  parts  in  place;  Fig.  30  (b),  the  die  with  one  part 


removed,  and  the  latter  being  shown  detached  in  Fig.  30  (c). 
This  die  can  be  adjusted  within  narrow  limits,  the  screw  d 
being  made  with  a tapered  head,  and  by  turning  it  in,  the 
two  halves  are  forced  apart. 

The  die  stock,  Fig.  31,  is  provided  with  a thumbscrew  that 
grips  the  die  when  in  place.  The  lower  part  r,  Fig.  30  (b),  of 
this  die  is  bored  out  to  the  exact  size  of  the  rod  to  be  threaded, 


C.  6".  III.— 15 


30 


BENCH,  VISE,  AND  FLOOR  WORK. 


21 


and  forms  a guide  for  the  die  in  starting.  These  dies  require 
some  pressure  to  start  them,  but  once  started  they  cut  a 
full  thread  at  one  operation.  The  large  sizes  are  made  with 
inserted  chasers  that  are  adjustable  for  wear  and  if  broken 
may  easily  be  replaced. 

50.  Pipework. — Pipework  enters  largely  into  some 
branches  of  machine  work,  and  a few  of  the  principal  tools 
used  in  this  connection  will  be  illustrated  and  described. 
Pipe  is  made  in  lengths  of  from  15  to  20  feet.  It  is  threaded 
on  both  ends  at  the  pipe  mill,  and  a sleeve  screwed  on  one 
end.  Large  pipe  has  a ring  screwed  on  the  other  end,  to 
protect  the  threads  during  shipment  and  handling. 

51.  Cutting  Pipe. — Large  pipe  is  generally  cut  into 
the  proper  lengths  in  a pipe-cutting  machine  by  a cutting-off 
tool,  in  the  same  manner  that  stock  is  cut  off  in  the  lathe, 
and  afterwards  is  threaded  in  the  same  machine.  Some 
pipe  machines  are  driven  by  hand,  others  by  power.  A 
great  deal  of  small  pipe  is  cut  with  a pipe  cutter,  shown  in 
Fig.  32.  The  body  c of  this  tool  carries  a slide  e , operated 
by  the  screw  on  the  handle  f.  Three  hardened-steel  cutting 
wheels  a , b , d are  set  in  the  frame  and  slide.  The  slide  e is 


drawn  back  by  means  of  the  screw,  to  allow  the  pipe  to  go  in 
between  the  cutters,  which  are  then  forced  into  the  pipe  by 
turning  the  handle,  and  at  the  same  time  rotating  the  tool 
around  the  pipe.  Other  cutters  of  this  sort  are  made  that 
have  but  one  cutting  wheel,  which  is  in  the  slide.  A hack 
saw  makes  a good  pipe  cutter,  if  used  carefully,  and  by  using 
blades  having  25  teeth  per  inch  there  is  little  danger  of 
breakage.  Thin  brass  and  copper  tubing  can  be  cut  easier 
by  a hack  saw  than  by  any  other  means. 


§21  BENCH,  VISE,  AND  FLOOR  WORK. 


31 


52.  Threading  Pipe. — When  the  pipe  is  cut  to  the 
correct  length,  it  must  be  threaded.  This  is  done,  as  has 
been  said,  in  power-driven  machines  for  the  large  sizes,  but 
most  of  the  small-pipe  threading  is  done  by  hand  with  one 
of  the  various  forms  of  pipe  dies. 


53.  Pipe  Stock. — The  ordinary  pipe  stock  is  shown  in 
Fig.  33.  This  stock  has  a body  d into  which  handles  c 


ia)  ( h > 

Fig.  33. 


are  screwed  at  each  end.  It  has  a square  recess  Fig.  33  (c), 
in  the  top  to  hold  the  die  a , Fig.  33  (a).  A cover  d , 
Fig.  33  ( d ),  slides  over  the  die  to  hold  it  in  place.  For 
threading  the  larger  sizes  of  pipe,  the  pipe  stock  is  threaded 
internally  and  the  bushing  e,  Fig.  33  (d),  is  screwed  into  it. 
The  thread  is  11^  per  inch  for  sizes  up  to  and  including 
2 inches,  and  above  that  8 per  inch,  to  correspond  to  the 
standard  pipe  threads.  A bushing,  or  thimble,  h having  a 


32 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


hole  through  it  of  the  size  of  the  outside  diameter  of  the 
pipe  is  placed  in  the  bushing  <?,  and  the  whole  slid  over  the 
end  of  the  pipe  so  that  the  cutting  edges  of  the  die  rest  on 
the  end  of  the  pipe.  The  bushing  e is  made  fast  to  the  pipe 
by  a setscrew  /"and^and  the  stock  given  a few  turns  to 
start  the  die  on  the  pipe,  the  screw  thread  in  the  stock  act- 
ing the  same  as  the  lead  screw  in  a lathe.  As  soon  as  the  die 
has  a good^start,  the  setscrew  holding  the  feeding  screw 
may  be  loosened,  and  the  work  finished  without  it.  The 
small  sizes  of  pipe  are  threaded  in  the  same  manner,  but 
the  die  stock  is  made  without  the  feed  or  lead  screw. 


54.  Adjustable  Die. — This  is  made  in  two  parts,  as 
shown  in  Fig.  ^4.  The  stock  is  provided  with  the  usual 
handles  for  turning  and  the  thimble  for  guiding  the  dies  on 
the  pipe.  The  dies  a are  held  in  the  stock  b by  means  of 
the  clamp  screws  c,  and  are  made  to  cut  larger  or  smaller 


FIG.  34. 

than  the  standard  by  the  adjusting  screws  d.  Lines  s are 
cut  in  the  stock,  and  corresponding  lines  s'  are  placed  on  each 
die,  so  that  when  these  lines  coincide  the  dies  are  set  to  cut 
pipe  to  the  standard  size.  These  dies  are  more  easily 
sharpened  than  are  the  solid  ones,  which  makes  them 
decidedly  superior. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


33 


PIPE  VISES  A1VI>  WRENCHES. 

55.  Pipe  Vises. — Pipe,  being  round,  cannot  be  screwed 
together  by  the  ordinary  forms  of  wrenches,  and,  being  hol- 
low, it  cannot  be  held  in  the  ordinary  vise  without  being 
crushed.  For  cutting,  threading,  or  having  fittings  screwed 
on,  pipe  may  be  held  in  a pipe  vise,  Fig.  10,  Part  1,  or  in 
an  ordinary  vise  having  clamps  made  in  the  form  shown  in 


Fig.  35.  The  holes  a in  this  clamp  are  made  to  fit  the  out- 
side diameter  of  the  pipe,  and  have  teeth  cut  in  them  to  pre- 
vent the  work  from  slipping.  They  are  held  together  by 
the  spring  b.  For  putting  polished  pipe  together,  some  form 
of  clamp  or  wrench  having  smooth  jaws  must  be  used. 

56.  Pipe  Tongs. — Ordinary  iron  pipe  is  screwed 
together  with  wrenches’  of  various  forms.  The  principal 
ones  are  shown  in  the  following  illustrations:  Fig.  36  shows 


Fig.  36. 


the  most  common  form,  commonly  called  pipe  tongs,  one 
size  being  provided  for  each  separate  size  of  pipe.  This 
general  style  is  also  made  with  the  jaw  a adjustable  and 
controlled  by  a screw,  so  as  to  adapt  one  pair  of  tongs  to 
several  sizes  of  pipe. 


34 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


The  chain  tongs  shown  in  Fig.  37  is  especially  adapted 
to  work  on  large  pipe.  The  handle  e has  two  steel  jaws  a 
cut  on  both  sides.  A chain  b made  fast  to  the  bolt  c per- 
mits both  sides  of  the  jaws  to  be  used.  Wrenches  of  this 


type  are  made  of  various  sizes  for  use  on  all  sizes  of  pipe. 
Chain  tongs  are  the  most  rapid  and  economical  tools  of  their 
kind  for  medium  and  large  work. 

57.  Pipe  Wrenches. — The  Stillson  pipe  wrench,  illus- 
trated in  Fig.  38,  is  an  adjustable  wrench.  It  has  a movable 
jaw  a moved  by  the  milled  nut  b,  and  may  be  used  on 


Fig.  38. 


several  sizes.  It  is  made  particularly  for  pipework,  but  finds 
many  other  useful  applications.  Alligator  wrenches  have 
a V-shaped  opening  in  one  end,  and  in  the  smaller  sizes  in 
both  ends.  One  side  of  this  opening  is  left  smooth  and  the 


Fig.  39. 


other  has  teeth  cut  across  it  in  the  form  shown  in  Fig.  39. 
These  wrenches  grip  all  round  objects,  and  are  used  to  grip 
pipe  in  places  where  the  other  forms  of  wrenches  can  get  no 
hold  at  all. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


35 


A wedge-shaped  piece  of  steel,  as  b,  Fig.  40,  having  teeth 
cut  on  it  similar  to  those  on  the  jaw  of  an  alligator  wrench, 
may  be  made  for  any  size  of  monkeywrench.  The  jaw  may 
be  made  in  the  form  of  a fork,  the  two  arms  of  which  reach 
past  the  bar  of  the  wrench  and  have  a hole  through  their 
ends,  so  that  a split  pin  can  be  put  through  them  to  keep  the 
jaw  from  falling  from  its  place  on  the  bar. 

Fig.  40  (a)  shows  a monkeywrench  having  a manufac- 
tured jaw  b on  its  bar.  This  jaw  differs  from  the  shop-made 
jaw  in  having  only  one  arm,  which  is  bent  at  right  angles  to 


pass  over  or  around  the  back  of  the  bar,  as  shown  at  c.  A 
thumbscrew  d is  used  in  this  jaw,  instead  of  the  pin,  to  hold 
it  on  the  bar. 

Fig.  40  (b)  shows  a simple  attachment  for  adapting  a 
monkeywrench  to  pipework.  This  consists  of  a nurled  and 
hardened  cylinder,  or  roller  having  a wire  handle  f for 
convenience  in  putting  it  in  place.  It  is  placed  between  the 
wrench  jaw  and  the  pipe,  or  other  round  piece,  as  shown 
at  g.  A piece-  of  10-inch  or  12-inch  round  file  about  1 or 
1^  inches  long  may  be  used  instead  of  this  attachment. 

58.  Use  of  Rope  as  Pipe  Wrench. — A rope  may  be 
used  in  place  of  a pipe  wrench,  if  a suitable  wrench  or  tongs 


36 


BENCH,  VISE,  AND  FLOOR  WORK. 


§21 


is  not  available.  The  manner  of  making  and  using  such  a 
device  is  shown  in  Fig.  41.  The  rope  is  first  doubled,  as 
shown  at  a,  and  given  enough  turns  round  the  pipe  to  insure 
gripping.  A bar  or  even  a piece  of  wood  bis  thrust  through 
the  double  end  of  the  rope  a , and  the  two  loose  ends  of  the 


rope  are  brought  together  and  held,  as  shown  at  c.  Enough 
strain  is  put  on  c to  prevent  slipping,  and  the  pipe  is  turned 
by  the  bar  b,  the  same  as  with  any  pipe  wrench.  The  work- 
man may  walk  around  the  pipe,  or  by  slacking  off  on  both 
the  bar  and  the  rope  ends,  he  may  rotate  the  rope  back- 
wards to  get  a new  hold. 


LAYING  OUT. 


INTRODUCTORY. 

59.  Definition. — Laying  out  is  the  process  of  placing 
such  lines  on  castings,  forgings,  or  partially  finished  surfaces 
as  will  designate  the  exact  location  and  nature  of  the  opera- 
tions specified  in  the  drawing. 

60.  Preliminary  Operations. — In  many  cases,  one 
or  more  men  are  regularly  employed  in  laying  out  work. 
Occasionally,  the  same  men  devote  a part  of  their  time  to 
inspecting  or  testing  finished  or  partly  finished  work.  The 


21 


BENCH,  VISE,  AND  FLOOR  WORK. 


37 


object  of  inspecting  when  partly  finished  is  to  prevent 
additional  work,  should  the  first  operation  be  defective  to 
a degree  that  calls  for  the  rejection  of  the  piece.  One  great 
advantage  of  having  the  work  laid  out  by  an  expert  who 
has  the  drawing  of  the  finished  piece  before  him  is  that  he 
may  determine,  before  any  work  is  done,  whether  the  for- 
ging or  casting  has  the  required  amount  of  stock,  and  should 
there  be  insufficient  stock  at  any  particular  point,  the  piece 
may  either  be  rejected  or  perhaps  saved  by  carefully  locating 
the  lines  so  as  to  permit  the  finishing  of  all  the  holes  and 
surfaces;  whereas,  if  a part  of  the  work  is  done  without  the 
special  laying  out,  it  may  afterwards  be  found  that  there  is 
not  sufficient  stock  for  some  later  operation. 

61.  Most  Economical  Method.— The  economy  of 
having  the  laying  out  done  by  men  set  apart  for  that  pur- 
pose is  due  to  several  reasons.  Men  become  expert  and 
quick  at  this  kind  of  work ; the  tools  of  the  shop  are  not 
idle  while  the  men  running  them  stop  the  machine  to  do  the 
laying  out,  as  was  formerly  the  case;  even  the  vise  hands 
are  saved  the  time  of  laying  out  their  work ; besides,  it  can 
be  done  on  a convenient  plate  with  proper  tools  to  better 
advantage  than  otherwise.  Then,  work  can  be  laid  out  as 
soon  as  the  castings  or  forgings  come  into  the  shop,  per- 
haps long  before  the  tools  are  at  liberty  to  finish  the  work, 
and  it  may  be  of  great  advantage  to  find  out  early  any  lack 
of  stock,  or  any  defect  that  may  cause  the  rejection  of  the 
piece,  or  any  change  that  is  to  be  made,  if  it  is  a forging. 
For  instance,  a casting  may  appear  to  be  all  right,  but  a 
hole  may  be  cored  too  large,  or  the  core  may  not  have  been 
set  correctly,  or  it  may  have  moved  in  the  mold.  After  lay- 
ing out  some  of  the  lines  and  making  sure  that  there  is 
stock  enough  for  finishing,  it  is  often  advisable  to  do  part 
of  the  finishing  before  completing  the  laying  out. 

62.  Divisions  of  Laying  Out. — Laying  out  may  be 

divided  into  two  parts:  the  preliminary  and  the  final.  The 
preliminary  laying  out  consists  in  measuring  the  piece  to 
see  that  it  is  of  the  proper  size  and  dimensions,  and  then 


38 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


drawing  such  lines  on  its  surface  as  will  show  where  the 
first  machining  operations  are  to  be  performed.  The  center 
lines  are  so  placed,  if  possible,  that  they  will  not  be  removed 
by  the  machining  process,  and  can  be  used  in  resetting  the 
piece  for  future  machining.  The  final  laying  out  consists 
of  placing  such  lines  on  the  machined  surfaces  as  will  indi- 
cate the  further  operations  to  be  performed. 

The  preliminary  laying  out  in  the  case  of  a steam-chest 
cover  would  be  to  level  it  on  the  table  and  draw  such  lines  on 
its  edges  as  will  indicate  its  thickness;  after  which  it  should 
go  to  the  planer  and  be  machined  to  the  dimensions  denoted 
by  the  lines.  The  final  laying  out  will  consist  of  laying  out 
the  holes  for  the  studs  and  such  other  operations  as  may 
be  designated  on  the  drawing. 

63.  Methods  of  Laying  Out. — Laying  out  is  done  in 
different  ways,  according  to  the  nature  of  the  work  and  the 
accuracy  required.  The  lines  are  drawn  on  the  surfaces 
with  surface  gauges  or  scribers,  and  centers  are  denoted  by 
prick-punch  marks.  Circles  and  arcs  of  circles  are  drawn 
with  dividers  and  trammels,  and  many  irregular  forms  are 
drawn  on  the  work  from  accurately  filed  templets. 

In  some  cases,  the  work  is  laid  out  by  simply  drawing  the 
necessary  lines  on  its  surface.  In  other  instances,  perma- 
nence is  given  the  lines  by  dotting  them  with  prick-punch 
marks  placed  directly  on  the  line;  or,  a thin  chisel  may  be 
driven  into  the  work  on  the  lines,  making  a deep  cut  in  the 
metal.  Guard  lines  are  often  placed  on  the  work  to  make 
sure  that  the  original  lines  were  closely  followed,  as,  in  lay- 
ing out  holes  to  be  drilled,  some  machinists  place  a circle 
Yg-  inch  outside  the  one  worked  to,  and  if  the  hole  is  correctly 
drilled,  it  will  be  concentric  with  this  circle. 

64.  Coatings  on  Which  to  Make  Lines. — In  many 
cases  it  would  be  impossible  to  scratch  lines  on  an  iron  sur- 
face, especially  when  the  latter  surface  is  not  perfectly 
smooth  or  when  it  is  very  hard.  This  has  led  to  the  use  of 
various  coatings,  on  which  the  lines  may  be  made  or  in  which 
they  may  be  scratched.  Sometimes,  chalk  is  simply  rubbed 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


39 


on  the  surface.  In  other  cases,  powdered  chalk  is  mixed 
with  alcohol  and  applied  with  a brush,  or  whiting  is  mixed 
with  alcohol  or  water  and  applied  in  the  same  way.  Alco- 
hol has  the  advantage  over  water  in  that  it  will  dry  quicker 
and  has  no  tendency  to  rust  the  surface. 

When  the  surface  has  been  machined  and  is  fairly  smooth, 
it  may  be  copper-plated  by  wetting  and  rubbing  the  surface 
with  a piece  of  copper  sulphate  (blue  vitriol),  or,  better  still, 
by  making  a saturated  solution  of  copper  sulphate  and 
applying  this  with  a brush  or  swab.  As  the  solution  dries, 
it  will  be  noticed  that  the  surface  is  covered  with  a thin 
layer  of  copper.  This  cannot  be  done  if  there  is  any  oil  on 
the  surface,  and  surfaces  to  be  thus  coppered  must  be 
cleaned  perfectly  before  applying  the  solution.  Lines  may 
easily  be  scratched  in  this  copper  and  will  show  very  plainly 
on  account  of  the  difference  in  color  between  the  iron  and 
the  copper.  In  some  cases,  a light  coat  of  some  quick- 
drying white  paint  is  used,  as,  for  instance,  white  lead  and 
turpentine.  In  any  case,  after  the  lines  are  drawn,  their 
location  should  be  permanently  established  by  means  of  light 
prick-punch  marks. 


LAYING-OUT  TOOLS. 

65.  Tools  and  Appliances  Used  in  Laying  Out. 

A variety  of  tools  are  used  in  laying  out  work.  The  most 
common  are  the  surface  gauge,  scriber,  hammer,  prick 
punch,  level,  square,  dividers,  trammels,  and  a line,  if  large 
work  is  handled.,  In  addition  to  these  tools,  there  should  be 
a supply  of  quick-drying  white  paint,  chalk,  a solution  of 
blue  vitriol,  a lot  of  iron  wedges,  and  small  pieces  of  sheet 
metal  of  various  thicknesses  for  blocking,  parallels  of  vari- 
ous sizes,  small  screw  jacks,  one  or  more  pairs  of  V blocks, 
a pinch  bar,  and  a hack  saw. 

The  surface  of  the  laying-out  table  or  plate  must  be  kept 
as  clean  as  possible;  therefore,  a bench  brush  should  be  pro- 
vided for  the  table,  and  for  the  large  plate,  a brush  and 
broom.  As  a good  many  drawings  are  used  at  the  laying- 
out  table,  a table  or  stand  of  sufficient  size  to  hold  them, 


40 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


and  drawers  in  which  to  place  those  not  in  constant  use, 
should  be  provided  near  at  hand. 

66.  Surface  Plates. — The  surface  plate  is  used  in 
machine  construction  for  testing  flat  surfaces.  It  is  gener- 
ally made,  as  shown  in  Fig.  42,  of  a hard,  close-grained  iron 
casting  having  a flat  top  a , Fig.  42  (< a ),  supported  by  a 
ribbed  back  b,  Fig.  42  (b).  Three  legs  c , d,  and  e,  Fig.  42  (b), 


Fig.  42. 


are  provided,  so  that  the  plate  will  stand  evenly  on  any  sur- 
face. Handles  /"  and  g are  placed  on  the  ends,  by  which  the 
plate  may  be  lifted.  The  tops  of  these  plates  are  first  planed 
as  smooth  as  possible,  after  which  they  are  filed  and  scraped 
perfectly  flat. 

When  in  use,  the  surface  plate  is  coated  lightly  with  some 
marking  material,  after  which  the  plate  is  rubbed  over  the 
surface  that  is  to  be  trued.  The  marking  material  is  left 
on  the  high  places,  thus  showing  the  parts  that  are  to  be 
removed  with  the  scraper.  This  operation  is  repeated  until 
the  surface  shows  a good  bearing  at  all  points.  Small  arti- 
cles are  rubbed  on  the  plate.  Care  should  be  taken  in  using- 
surface  plates  to  use  every  part  of  the  surface  as  evenly  as 
possible,  for  if  the  work  is  all  done  in  one  place,  the  plate 
will  soon  be  spoiled.  Surface  plates  of  this  form  are  made 
in  a great  variety  of  sizes  for  different  kinds  of  work.  Spe- 
cial plates  are  often  made  for  special  work,  in  places  where 
it  is  impossible  to  put  a plate  having  a ribbed  back. 

67.  Straightedges. — A straightedge  is  used  for  test- 
ing flat  surfaces  and  the  alinement  of  machine  parts.  Most 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


41 


straightedges  are  made  with  two  edges  that  must  be  straight 
and  parallel.  The  metal  of  the  straightedge  must  be  so 
placed  as  to  give  the  greatest  stiffness  in  the  direction  of 
the  edge  to  be  used.  For  this  reason,  straightedges  are 
usually  made  deeper  than  they  are  wide.  Straightedges  are 
made  in  a large  variety  of  forms  and  lengths,  and  may  vary 
from  1 inch  or  so  in  length  up  to  10  feet  or  more. 

For  small  work,  a graduated  steel  rule  is  frequently  used 
as  a straightedge,  the  hardened  and  ground  ones  produced 
by  several  manufacturers  be- 
ing the  best  for  this  purpose. 

Hardened-steel  straightedges 
having  the  general  form  of 
a knife,  so  as  to  reduce  the 
straightedge  to  a narrow  line,  are  frequently  used.  Fig.  43 
illustrates  a common  form  that  is  hollowed  out  on  the  sides 
so  as  to  give  a better  grip  to  the  hand  in  using  it. 

68.  Long  Straightedges. — Where  straightedges  of 
considerable  length  are  desired,  careful  attention  should  be 
paid  to  their  design,  to  see  that  they  are  made  as  stiff  as 
possible,  and  at  the  same  time  that  the  weight  is  not  unduly 
increased.  Where  only  one  straight  surface  is  required,  the 
form  shown  in  Fig.  44  is  very  good  indeed.  These  are  made 
of  cast  iron,  and  the  surface  a b is  carefully  planed  and  scraped 


true.  Where  it  is  necessary  to  use  a level  on  the  back  of 
the  straightedge,  or  where  other  straightedges  may  have  to 
be  placed  at  right  angles,  it  becomes  necessary  to  have  both 
edges  true  and  parallel.  For  this  class  of  work  the  tool 
shown  in  Fig.  45  is  especially  useful.  The  drawing  shows 
the  proportions  for  a 10-foot  straightedge.  It  will  be  noticed 
that  the  general  form  is  that  of  a box  girder,  and  that  the 


42 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


center  is  cored  out,  openings  being  left  in  the  sides  to  sup- 
port the  core  during  casting.  The  metal,  in  the  case  of  a 
10-foot  straightedge,  should  be  about  \ inch  thick,  and  a 

a 


straightedge  of  this  form  should  be  planed  all  over  and 
allowed  to  season  some  time  before  it  is  finished,  so  as  to 
relieve  the  casting  strains  as  much  as  possible. 


b 

Fig.  45. 


SUBDIVIDING  CIRCLES. 

69.  Locating  the  Centers  of  Circles. — When  it  is 
necessary  to  draw  a circle,  on  work  where  the  center  does 
not  occur  on  the  casting,  but  in  the  center  of  an  opening  or 
cored  hole,  it  is  necessary  to  locate  the  center  from  which 
the  circle  may  be  drawn.  This  may  be  done  by  fitting  a 
strip  of  wood  across  the  cored  opening,  and  locating  the 
center  on  this.  Owing  to  the  fact  that  wood  is  too  soft 
to  give  a good  center  to  work  from,  it  is  usual  to  place  a 
piece  of  metal  where  the  center  is  required.  This  piece  of 
metal  may  be  a tack  driven  into  the  wood,  the  center  being 
located  on  the  head;  or  it  may  be  a triangular  piece  of  tin 
having  the  corners  bent  at  right  angles  to  the  surface,  so 
that  they  can  be  driven  into  the  wood,  the  center  being 
located  on  the  flat  surface  of  the  tin. 

70.  Use  of  Screw  Jacks. — Sometimes,  small  screw 
jacks  having  flat  sides  on  the  body  of  the  jack  are  used 
to  locate  centers,  the  screw  jack  being  placed  across  the  hole 
and  the  center  located  on  its  side,  as  shown  in  Fig.  46  (a). 
After  the  center  is  located,  the  bolt-hole  circle  is  drawn, 
and  the  required  holes  spaced  off  on  it.  If  the  cored  hole  is 
too  large  for  one  screw  jack  to  reach  across,  two  screw  jacks 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


43 


may  be  placed  with  their  bases  together,  as  shown  in 
Fig.  46  (b),  and  the  center  located  on  them. 


71.  Laying  Off  Subdivisions  of  a Circle. — In  case 
a circle  is  to  be  divided  into  4 or  6 parts,  or  into  multiples 
of  4 or  6 parts,  it  is  usual  to  draw  diameters  dividing  it  into 
this  number  of  parts  first,  and  then  make  any  additional  sub- 
divisions from  these  points.  Four  divisions  can  be  easily 
obtained  by  drawing  two  diameters  at  right  angles,  the 
work  being  mounted  on  the  laying-out  plate,  the  horizontal 
diameter  being  obtained  with  the  surface  gauge,  and  the 
vertical  one  by  means  of  a square. 

To  produce  6 divisions,  it  is  only  necessary  to  set  the 
dividers  to  the  radius  of  the  circle  and  then  step  them 
around  the  circumference  of  the  circle,  when  it  will  be 
found  that  the  radius  will  just  step  around  6 times.  In 
order  to  produce  any  other  number  of  divisions,  up  to  and 
including  100,  the  accompanying  table  is  given.  By  its  use, 
the  dividers  may  be  set  very  closely,  and  much  of  the  time 
and  trouble  usually  spent  in  getting  the  dividers  properly 
set  by  stepping  them  around  with  trial  distances  may  be 
avoided.  The  numbers  in  the  column  headed  “N  ’’indicate 
the  number  of  divisions  into  which  the  circle  is  to  be  divided, 
and  the  numbers  in  the  column  headed  “ S ” are  the  sines  of 


44 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


TABLE  FOB  DIVIDING  CIRCLES. 


N 

S 

N 

S 

N 

S 

N 

S 

i 

26 

. 1 20540 

5i 

. 061560 

76 

.041325 

2 

27 

. 1 16090 

52 

•060379 

77 

. 040788 

3 

. 86603 

28 

. 1 1 1970 

53 

•059240 

78 

. 040267 

4 

. 707 1 1 

29 

. 108120 

54 

•058145 

79 

•039757 

5 

• 58779 

30 

• 104530 

55 

•057090 

80 

. 039260 

6 

. 50000 

3i 

. 101 1 70 

56 

.056071 

81 

•038775 

7 

• 43388 

32 

. 098018 

57 

•055089 

82 

•038303 

8 

.38268 

33 

•095056 

58 

•054139 

83 

•037841 

9 

.34202 

34 

. 092269 

59 

•053222 

84 

•037391 

IO 

.30902 

35 

. 089640 

60 

•052336 

85 

•°36953 

1 1 

.28173 

36 

.087156 

61 

•051478 

86 

•036522 

12 

. 25882 

37 

. 084804 

62 

•050649 

87 

•036103 

i3 

.23932 

38 

. 082580 

63 

•049845 

88 

.035692 

i4 

.22252 

39 

. 080466 

64 

. 049068 

89 

•035291 

15 

. 20791 

40 

. 078460 

65 

.048312 

90 

•034899 

16 

.19509 

4i 

.076549 

66 

.047582 

9i 

.034516 

17 

■i8375 

42 

.074731 

67 

. 046872 

92 

.034141 

18 

•i7365 

43 

•072995 

68 

. 046184 

93 

•033774 

19 

. 16460 

44 

•071339 

69 

•045515 

94 

•033415 

20 

•15643 

45 

•069756 

70 

•044865 

95 

•033064 

2 1 

. I49°4 

46 

. 068243 

7i 

•044232 

96 

•032719 

22 

.14232 

47 

•066793 

72 

•0436i9 

97 

.032381 

23 

• 1 36 17 

48 

. 065401 

73 

.043022 

98 

•032051 

24 

•13053 

49 

•064073 

74 

. 042441 

99 

. 031728 

25 

•12533 

5° 

. 062791 

75 

.041875 

100 

.031411 

half  the  angles  obtained  by  dividing  the  circle  into  the  number 
of  parts  given  in  N.  The  distance  between  any  two  points 
on  the  circle  may  be  obtained  by  the  formula  M — 5 X Dt 
in  which  M equals  the  measured  distance  between  two  of 
the  points  in  inches,  D the  diameter  of  the  circle  in  inches, 
and  5 the  number  found  in  the  column  S of  the  table  oppo- 
site the  number  of  holes  required. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


45 


Example. — If  it  is  required  to  divide  a 62-inch  circle  into  44  equal 
parts,  what  will  be  the  distance  to  which  the  dividers  should  be  set  ? 

Solution. — Opposite  44  in  the  column  marked  N of  the  table,  and 
in  the  column  marked  S,  is  found  .071339.  Substituting  in  the  for- 
mula, we  have 

M = .071339  X 62  = 4.423018  in.  Ans. 

For  ordinary  work  it  would  not  be  necessary  to  set  the  dividers 
closer  than  to  hundredths  of  an  inch ; hence,  the  dividers  may  be  set 
to  4.42  inches.  On  account  of  the  fact  that  44  is  divisible  by  4,  the 
circle  may  be  divided  by  two  diameters  drawn  at  right  angles,  and  the 
spaces  marked  off  to  the  four  points  thus  obtained. 

72.  Laying  Out  the  Square  and  Hexagon. — It  is 

always  best  in  laying  off  a circle  to  locate  either  4 or  6 
points  accurately  and  to  work  from  these,  as  this  reduces 
the  effect  produced  by  means  of  a slight  mistake  in  the 
setting  of  the  dividers;  for  if  the  circle  were  all  laid  off  from 
one  point,  and  the  dividers  were  set  to  a distance  slightly 
greater  than  that  required,  the  last  division  would  be 
smaller  than  the  others  by  an  amount  equal  to  this  error 
multiplied  by  the  number  of  spaces  in  the  circle.  But  by 
dividing  the  circle  into  4 or  6 parts,  and  then  stepping  off 
the  spaces  each  way  from  each  of  these  points,  the  total 
error  at  any  given  point  will  only  amount  to  the  error  in 
setting  the  dividers  multiplied  by  the  number  of  spaces 
marked  off  from  the  given  point,  which  will  be  from  -J-  to 
of  that  in  the  previous  case,  depending  on  whether  the  circle 
has  been  divided  into  4 or  6 parts. 


LAYING-OUT  PLATES. 

73.  Plate  for  Light  Work. — For  laying  out  light 
or  small  work,  the  size  and  character  of  the  plate  used  may 
vary  greatly.  In  some  cases  a flat  casting,  as  the  base  of 
an  old  machine,  is  taken  from  the  scrap  pile  and  planed  up; 
this  is  placed  on  a bench  or  on  suitable  trestles.  In  other 
cases,  a well-designed  casting  is  made.  Fig.  47  illustrates 
a general  form  of  laying-out  plate.  The  plate  a may  vary 
in  size  from  2 or  3 feet  on  each  side  up  to  considerable 


C.  S.  III. — 16 


46 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


size,  about  7 feet  by  10  feet  being  the  largest  size  practicable 
for  this  design  of  plate.  In  the  larger  size,  the  top  a should 
be  made  1^  inches  thick,  the  ribs  b should  be  carried  around 
the  sides  of  the  plate  and  cross-ribs  placed  across  the  back 
of  the  plate  about  every  24  inches;  the  depth  of  these  ribs 
for  a plate  7 feet  by  10  feet  should  not  be  less  than  8 inches, 
and  they  should  be  of  the  same  thickness  as  the  body  of  the 
plate.  The  casting  should  be  planed  on  the  upper  surface# 
and  on  the  faces  of  the  ribs  b , so  that  the  faces  b will  be  at 
right  angles  to  the  surface  #,  thus  ijiaking  it  possible  to  use 
surface  gauges  or  other  tools  from  the  faces  b.  In  a plate 


of  this  style,  it  is  well  to  draw  parallel  lines  both  lengthwise 
and  crosswise  of  the  plate,  the  lines  being  3 or  6 inches 
apart.  As  shown  in  the  illustration,  the  plate  is  mounted 
on  trestles  c , and  care  should  be  taken  to  keep  the  upper 
surface  of  the  plate  level  and  out  of  wind,  by  adjusting 
wedges  under  the  legs  of  the  trestles,  as  shown  at  d.  For 
ordinary  working,  it  is  well  to  have  the  upper  surface  of  the 
plate  about  30  inches  from  the  floor.  Such  a plate  as  this 
may  be  placed  under  the  main  traveling  crane,  and  it  is  also 
well  to  have  an  auxiliary  air  lift,  or  similar  hoisting  device, 
for  handling  the  work  when  the  crane  is  not  available. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


47 


74.  The  advantages  of  this  style  of  plate  are  that  it  is 
not  a permanent  fixture  in  any  one  place,  and  hence  can  be 
easily  moved  from  one  part  of  the  shop  to  another,  if  it 
should  be  more  advantageous  to  have  it  in  a different 
position.  Then,  too,  if  the  plate  is  not  needed  for  some 
time,  but  the  floor  space  is,  it  can  be  turned  up  on  one  edge 
and  set  against  the  wall,  and  the  space  that  it  formerly 
occupied  utilized  for  erecting  or  for  other  work. 

75.  The  disadvantages  of  this  style  of  plate  are  that 
owing  to  its  support  on  trestles  it  is  not  suitable  for  laying 
off  heavy  work  that  requires  great  accuracy,  on  account 
of  the  fact  that  it  is  impossible  to  keep  the  plate  true  and 
out  of  wind  when  heavy  weights  are  being  placed  on  or 
taken  from  it,  as  the  stresses  on  both  the  plate  and  the  trestles 
are  constantly  changing.  Sometimes,  a plate  of  this  general 
style  is  mounted  on  a concrete  or  brick  foundation,  but  if 
the  latter  expense  is  to  be  incurred,  it  is  usually  best  to  have 
a more  elaborate  one,  such  as  is  described  in  Arts.  76 
and  77. 

76.  Plate  for  Heavy  Work. — For  laying  off  heavy 
work,  the  plate  must  have  a very  firm  foundation,  and  the 
ribs  must  be  of  such  a depth  that  there  is  no  danger  of 
the  plate  springing  under  the  weight  of  the  piece  being  laid 
off.  Plates  for  heavy  work  are  usually  made  lower  than 
those  for  light  work,  the  top  of  the  plate  being  placed  from 
18  to  24  inches  above  the  floor.  Fig.  48  illustrates  a very 
good  plate  for  heavy  work  that  is  in  use  in  one  large  shop. 
The  top  of  this  plate  is  24  inches  above  the  floor,  and  it  is 
composed  *of  two  pieces  A and  B that  are  joined  together 
with  a tongue  and  groove,  as  shown  at  C.  This  plate  is 
8 feet  by  15  feet,  and  the  ribs  around  the  outside  and  along 
the  center  are  made  to  extend  clear  to  the  foundation, 
which  is  only  2 inches  above  the  floor,  thus  making  the  plate 
22  inches  deep.  Parallel  grooves  6 inches  apart  are  planed 
the  entire  length  of  the  top  surface,  and  at  right  angles  to 
these  lines  are  ruled  on  the  surface  6 inches  apart.  The 
grooves  are  especially  handy,  on  account  of  the  fact  that 


48 


BENCH,  VISE,  AND  FLOOR  WORK. 


21 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


49 


parallels  can  be  slipped  into  them  and  pieces  brought 
against  these  parallels  for  lining  up,  after  which  measure- 
ments may  be  made  from  either  grooves  or  lines.  In  the 
case  of  all  heavy  plates,  care  should  be  taken  to  see  that  the 
plate  has  a good  bearing  on  the  foundation,  and  that 
the  foundation  is  made  deep  and  strong  enough  that  it  will 
not  settle  or  be  broken  under  any  weight  that  is  liable  to  be 
put  on  the  plate. 

77.  Plate  for  General  Work.  — In  shops  handling 
a variety  of  work,  varying  from  heavy  to  light,  a plate  of 


Fig.  49. 

the  form  illustrated  in  Fig.  49  may  be  used.  This  plate  is 
about  8 feet  by  12  feet,  and  the  details  are  shown  in  Fig.  50. 


Fig.  50. 

The  foundation  consists  of  a concrete  base  on  which  are 
built  three  brick  walls  running  lengthwise  of  the  plate  and 


50 


BENCH,  VIvSE,  AND  FLOOR  WORK.  § 21 


a cross-wall  at  each  end.  The  plate  is  supported  on  these 
walls,  as  shown  in  Fig.  50.  A hole  in  the  plate,  at  least 
18  inches  by  24  inches,  together  with  an  opening  in  the 
middle  wall,  affords  access  to  the  space  beneath  the  plate  for 
the  purpose  of  cementing  between  the  iron  and  brickwork. 
This  hole  in  the  plate  is  also  useful,  on  account  of  the  fact 
that  it  permits  parts  of  the  work  to  hang  below  the  surface ; 
as,  for  instance,  one  crank  of  a three-throw  crank,  or  an 
arm  on  a rocker-shaft.  The  hole  is  cast  with  a ledge  to 
receive  a wooden  cover.  This  cover  is  necessary  to  prevent 
objects  from  falling  through  the  hole  and  being  lost  under 
the  plate.  The  top  of  the  wooden  cover  should  be  inch 
below  the  surface  of  the  plate.  It  will  be  noticed  that  the 
plate  overhangs  the  foundation  7 inches  all  around,  to  allow 
foot-room  on  the  floor. 

Grooves  \ inch  wide  and  J-  inch  deep  are  planed  length- 
wise every  6 inches,  and  lines  made  crosswise  every  6 inches; 
or  grooves  may  be  planed  both  lengthwise  and  crosswise. 
A number  of  short  parallels  ^ inch  square  should  be  pro- 
vided to  drop  into  the  grooves  to  aid  in  locating  the  work 
or  tools.  The  proportions  or  size  of  the  plate  may,  of 
course,  be  varied  to  suit  the  character  of  the  work  being 
done.  It  is  not  good  practice  to  mount  a plate  on  brick 
walls  all  running  in  one  direction,  when  heavy  work  is  to  be 
placed  on  or  taken  off  the  plate ; for  if  work  were  to  strike 
the  end,  there  would  be  danger  of  racking  the  walls,  while' 
the  tying  of  the  longitudinal  walls  together  at  the  ends  tends 
to  overcome  this  difficulty,  and  also  prevents  dirt  from  col- 
lecting beneath  the  plate. 

78.  Revolving  Laying-Out  Plate.— In  many  cases 
it  is  quite  important  to  have  the  light  fall  on  the  work 
from  a certain  direction,  so  as  to  enable  the  operator  to  see 
the  lines  being  drawn,  and  also  in  the  case  of  small  work,  it 
is  often  necessary  to  operate  on  several  sides  of  the  piece. 
If  this  work  were  placed  on  a large  plate,  the  work  would 
have  to  be  turned  and  reset  several  times,  or  the  operator 
would  have  to  climb  around  over  the  plate.  To  overcome 


21 


BENCH,  VISE,  AND  FLOOR  WORK. 


51 


this  difficulty,  a plate  of  the  general  form  shown  in  Fig.  51 
may  be  employed.  This  consists  of  a circular  table  a 


mounted  on  a suitable  foot,  or  base,  b.  The  back  of  the 
plate  a is  ribbed,  as  shown  in  Fig.  52,  and  a ball  bearing  is 
inserted  between  the  plate  a and  the  base  b , as  shown  at  c. 


In  order  to  facilitate  the  centering  of  work  having  a hole 
in  it,  a plug  d , Fig.  51,  may  be  inserted  in  the  center  of  the 


52 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


table  and  a ring  e of  suitable  diameter  placed  over  the  plug. 
Work  thus  dropped  over  a ring  of  the  proper  size  can  be 
quickly  centered.  To  facilitate  the  dividing  of  work,  two 
grooves  f and  g are  planed  across  the  table  at  right  angles. 
These  grooves  are  so  located  that  one  edge  of  the  groove 
passes  through  the  center  of  the  table.  For  convenience  in 
measuring,  other  grooves  may  be  located  at  any  specified 
distances  from  the  center,  and  parallel  to  either  one  of  the 
main  grooves,  as  shown  at  h.  Small  parallels  are  introduced 
into  the  grooves  for  adjusting  squares  or  other  tools,  or 
to  bring  the  work  into  the  desired  position.  These  parallels 
are  shown  in  position  at  i,  i.  By  means  of  these  two  grooves 
and  the  parallels,  work  can  very  quickly  be  divided  into 
four  equal  parts  by  dropping  the  parallels  into  the  grooves, 
and  bringing  a square  against  the  sides  of  the  parallels  in 
contact  with  the  edges  of  the  grooves  that  pass  through  the 
center  of  the  plate.  The  top  of  the  table  illustrated  is 
31  inches  above  the  floor,  and  the  rim  is  2 inches  thick.  For 
some  classes  of  work  it  is  convenient  to  have  circular  lines, 
1 inch  apart,  turned  on  the  table  before  the  plate  is  taken 
from  the  lathe. 

This  form  of  table  can  be  easily  taken  to  the  work,  in 
place  of  bringing  the  work  to  the  table,  in  cases  where  there 
is  a large  amount  to  be  handled,  and  especially  when  it  is 
advantageous  to  have  it  done  near  the  same  machine.  For 
convenience  in  moving  the  table,  an  extension  of  the  hole 
that  receives  the  pin  d in  the  base  b may  be  tapped,  and  a 
strong  eyebolt  fitted  to  it.  This  bolt  will  form  a ready  means 
of  attaching  the  crane  hook  to  the  table. 

79.  Special  Laying-Out  Appliances. — On  the  lay- 
ing-out table  illustrated  in  Fig.  48  are  shown  several  special 
laying-out  appliances.  First  may  be  mentioned  the  parallel 
shown  at  m . These  parallels  are  made  in  various  heights, 
differing  by  even  feet,  and  smaller  solid  parallels  or  hollow 
rectangular  parallels  are  made,  varying  by  inches,  so  that 
any  height,  varying  by  inches,  can  be  obtained  from  a series 
of  them.  The  edges  n and  /,  and  r and  ^ should  be  in  the 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


53 


same  vertical  planes,  so  that  when  one  of  the  edges  n or  r is 
brought  against  a certain  parallel  or  line  on  the  plate,  the 
corresponding  edge  p or  s will  be  in  the  same  vertical  plane. 
This  enables  the  man  doing  the  work  to  obtain  horizontal 
measurements  from  the  edges  of  the  upper  surfaces  of  the 
parallels.  With  the  use  of  these  parallels,  it  is  unnecessary 
to  use  the  old-fashioned  high  surface  gauge,  which  could 
never  be  depended  on  because  of  the  spring  of  its  parts. 

At  the  front  of  the  plate  are  shown  two  V blocks  o , o that 
are  extremely  useful  in  laying  out  pieces  having  turned 
ends,  or  any  form  that  has  to  be  supported  in  this  manner. 
At  h is  shown  a special  T square,  which,  for  some  classes 
of  work,  is  more  useful  than  an  ordinary  square  for  drawing 
vertical  lines,  owing  to  the  fact  that  there  is  little,  if  any, 
danger  of  the  portion  in  contact  with  the  plate  becoming 
displaced ; while  if  an  ordinary  square  were  used,  it  would 
be  necessary  to  make  the  arm  or  beam  in  contact  with  the 
plate  very  heavy  to  balance  the  long  blade. 


EXAMPLES  OF  LAYING  OUT. 

80.  Laying  Out  Bolt  Holes  for  Pipe  Flanges. 

In  Fig.  48  at  the  right-hand  side  of  the  plate  is  shown  a 
casting  for  a branch  pipe  in  which  it  is  required  to  lay  out 
bolt  holes  for  the  different  flanges.  The  pipe  is  leveled  by 
blocking  up  the  small  end  t until  the  large  end  a stands 
square  with  the  plate  or  table.  The  .branch,  or  arm,  u is 
next  raised  until  the  surface  b is  square  with  the  table. 
Wooden  strips  are  fitted  across  the  ends  of  the  pipe,  as 
shown  at  c , this  fitting  usually  being  done  before  leveling 
up  the  pipe,  so  as  not  to  displace  the  setting  by  driving  in  the 
wooden  strips.  After  the  wooden  strips  are  in  place  and  the 
pipe  is  leveled  up,  the  trammels  are  set  to  approximately 
the  radius  of  the  circle  e that  has  been  turned  on  the  end  of 
the  pipe  while  in  the  machine.  With  these  trammels,  the  arcs 
at  d are  drawn  and  a center  located  between  them.  Usually, 
a small  piece  of  tin  or  other  metal  is  placed  at  the  center 
of  the  wooden  strip,  to  receive  the  center  when  located. 


54 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


After  this,  trammels  or  dividers  are  set  to  the  radius  of  the 
bolt  circle  /"and  this  circle  drawn.  If  the  drawing  calls  for 
an  even  number  of  holes,  a surface  gauge  is  set  to  the 
center  and  a line  drawn  across  the  flange,  as  shown  at  v x. 
This  line  may  be  continued  across  all  three  of  the  flanges. 
If  the  number  of  holes  is  a multiple  of  4,  a vertical  line  is 
also  drawn  by  means  of  a square,  or  a T square  similar  to 
that  shown  at  /*,  thus  locating  the  top  and  bottom  holes  y 
and  z.  The  other  holes  are  spaced  off  from  these  by  means 
of  dividers.  In  case  of  any  number  of  holes,  whether  odd  or 
even,  the  setting  of  the  dividers  can  be  obtained  by  the 
method  described  in  Art.  71.  In  the  illustration,  12  holes 
are  shown  in  the  flange  a.  When  the  holes  in  the  three 
flanges  must  have  some  fixed  relation  to  one  another,  the 
horizontal  line  v x is  carried  around  all  three  faces,  and  the 
holes  laid  off  from  this  as  required. 


81.  Laying  Out  a Large  Journal  Cap. — At  the 

left-hand  corner  of  the  plate,  Fig.  48,  is  shown  a journal  cap 
in  the  process  of  being  laid  off.  The  casting  is  blocked 
up  on  the  plate  so  that  the  front  and  back  faces  are  approxi- 
mately square  to  the  surface,  and  the  center  line  i is  drawn 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


55 


midway  between  the  points  j\j.  The  shoulders  k , k are  laid 
off  at  equal  distances  from  the  center  line  i,  and  a proper 
allowance  for  finish  is  made  at  the  top  of  the  box,  after 
which  the  lines  /,  l are  drawn,  so  that  the  vertical  distance 
from  the  horizontal  plane  passing  through  /,  / to  the  point 
determined  at  the  top  of  the  box  is  equal  to  the  radius  of  the 
finished  box.  The  lines  <7,  q on  the  flanges  of  the  cap  are  next 
drawn  the  proper  distance  above  the  lines  /,  /.  After  this, 
the  cap  is  planed  before  the  holes  for  bolting  down  the  cap 
are  laid  out  or  drilled. 


82.  Laying  Out  a Crank-Arm.  — The  crank-arm 
shown  in  Fig.  53  may  be  laid  out  as  follows:  The  piece  is 
first  placed  on  its  side,  with  the  parallel  a under  the  small 


end.  A surface  gauge  is  set  to  the  center  of  the  hub,  which 
has  been  determined  by  placing  a wooden  strip  g across  the 
hub  and  locating  a center  h on  it  by  means  of  dividers. 
After  this,  the  parallel  a is  pushed  under  the  end  of  the  arm 


56 


BENCH,  VISE,  AND  FLOOR  WORK. 


21 


until  the  small  end  is  raised  so  that  the  point  of  the  dividers 
is  level  with  the  center  of  the  arm.  Then  the  line  b b'  b"  is 
drawn.  After  this  the  arm  is  clamped  to  an  angle  plate,  as 
shown  in  Fig.  54,  the  line  b b'  being  brought  vertical  by 
means  of  a square.  The  surface  gauge  is  set  to  the  center^ 
and  the  line  cc'  drawn.  The  surface  gauge  is  next  set  so 
that  its  point  will  be  above  the  line  c c'  an  amount  equal  to 
the  distance  between  the  two  holes  in  the  arm,  and  the 
line  d d'  is  drawn.  This  locates  the  center  of  the  hole  f,  after 
which  the  circles  at  e and  f may  be  drawn  with  dividers  and 
marked  off  with  prick-punch  marks,  as  shown,  ready  for 
drilling  or  boring. 

83.  laying  Out  a Crossliead. — The  method  of  lay- 
ing out  a crosshead  is  governed  principally  by  the  design 
of  the  crosshead.  The  form  shown  in  Fig.  55  is  one  provided 


with  adjustable  shoes,  the  end  hh!  of  the  crosshead  being 
considerably  narrower  than  the  end  a a' , so  that  as  the  shoes 
are  moved  along  on  these  inclined  surfaces  they  will  be 
expanded.  The  method  of  laying  out  is  as  follows : The  cross- 
head is  placed  on  the  table,  with  blocking  under  the  piston- 
rod  end,  and  wedges  under  both  sides  of  the  connecting-rod 
end,  as  shown  in  the  illustration.  If  the  piston-rod  end  is 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


57 


to  be  turned  at  the  part  marked  d , the  casting  is  usually 
made  with  a metal  bridge  which  is  cut  out  after  the  rest 
of  the  machine  work  has  been  done.  In  case  no  such  metal 
bridge  exists,  it  is  necessary  to  insert  a wooden  strip  at  this 
point  on  which  to  locate  the  center  f.  Wooden  blocks  are 
also  placed  in  the  holes,  as  shown  at  e,  and  in  the  center  of 
the  piston-rod  hole  in  the  end  d. 

Chalk  or  white  paint  is  applied  in  a broad  line  wherever 
the  laying-off  lines  are  to  be  placed,  as  shown  by  the' broad, 
dark  marks  in  the  illustration.  The  centers  of  the  holes  for 
the  connecting-rod  pin  and  for  the  piston  rod  are  now  found, 
and  the  casting  is  leveled  up  by  them  and  brought  square 
with  the  table  at  the  connecting-rod  end.  If  it  is  found  that 
the  cored  holes  for  the  piston-rod  or  crosshead  pin  are  not 
in  the  correct  relative  position,  the  body  of  the  casting  may 
be  shifted  somewhat,  to  bring  them  into  such  a location  that 
all  can  be  finished  to  the  required  dimensions.  When  these 
points  are  definitely  located,  the  center  line  ij  is  drawn  on 
all  sides  of  the  work.  The  centers, at  each  end  of  the  cross- 
head pinholes  e are  laid  off  the  proper  distance  from  the 
piston-rod  end  d , and  a circle  is  drawn  at  each  end  of  the 
cross-head  pin.  A circle  is  also  drawn  for  the  piston-rod 
hole.  The  slot  g for  the  piston-rod  key  is  next  laid  off  the 
proper  distance  from  the  end  d.  This  slot  is  sometimes 
made  with  round  ends  and  sometimes  with  square  ends, 
depending  on  the  conditions  specified  in  the  drawing. 

The  line  a a'  is  drawn  the  correct  distance  from  the  cen- 
ter e,  this  line  being  located  by  means  of  a square  that  is  set 
on  the  table.  The  lines  a h and  a’  h'  are  not  parallel  to  the 
table,  on  account  of  the  tapered  form  of  the  crosshead  body, 
and  in  order  to  determine  these  lines,  the  following  process 
may  be  used:  The  taper  is  usually  given  as  so  much  per 
foot  on  the  drawing,  and  this  amount  may  be  marked  off 
from  a and  a' , as  shown  at  b and  b' . After  this,  short  ver- 
tical lines  are  located  at  c and  cr,  1 foot  from  the  line  a a' , 
and  the  surface  gauge  is  set  to  the  point  b,  and  a mark  made 
at  c.  It  is  then  set  to  b\  and  the  mark  made  at  c',  thus 
establishing  two  points  on  the  inclined  lines.  After  this 


Fig. 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


59 


a straightedge  may  be  laid  through  the  points  a and  c and 
the  line  ah  drawn,  and  then  through  the  points  a' c'  and  the 
line  a'  h drawn.  The  lugs  k must  be  drilled  for  screws  to 
operate  the  crosshead  shoes.  These  screw  holes  may  be 
located  by  drawing  horizontal  lines  on  the  piston-rod  end  of 
the  lugs  by  means  of  the  surface  gauge.  These  lines  must 
be  the  proper  distance  from  the  center  line  of  the  crosshead. 
After  this,  the  center  of  the  lugs  may  be  found  by  means 
of  dividers,  and  the  circles  representing  the  holes  laid  out. 

84.  Laying  Out  an  Engine  Bed. — The  method  of 
laying  out  an  engine  bed  differs  according  to  the  type  of 
bed,  but  the  essential  features  of  the  process  are  the  same. 
Usually,  the  work  has  to  be  done  in  two  or  three  operations, 
owing  to  the  fact  that  some  of  the  surfaces  have  to  be 
machined  before  the  last  part  of  the  laying  out  can  be  done. 

The  bed  chosen  for  illustration  is  shown  in  Fig.  56  and  is 
of  the  solid  cast  variety,  having  bored  guides,  the  bearing  for 
the  crank-shaft  being  cast  solid  with  the  bed  . and  the  cylinder 
being  arranged  to  bolt  to  the  end  of  the  bed.  The  bed 
casting  a is  placed  on  the  laying-out  or  machine  table,  right 
side  up,  with  blocks  under  it  at  intervals,  as  shown  at  b,  b. 
Wooden  strips  are  fitted  across  the  ends  of  the  guides,  as 
shown  at  r,  and  across  the  sides  of  the  jaws  for  the  crank- 
shaft bearing,  as  shown  at  c.  The  centers  of  the  guides  are 
located  on  the  wooden  strips  at  both  ends,  and  those  of  the 
jaws  at  both  sides.  The  bed  is  now  tested  with  the  surface 
gauge,  and  set  level  by  driving  wedges  between  the  bed  and 
the  blocks  b.  If  either  of  the  points  located  does  not  come 
true,  the  centers  may  be  shifted  slightly,  care  being  taken 
to  allow  stock  enough  so  that  the  guides  and  the  jaws  of 
the  main  bearing  can  be  finished.  Some  beds  of  this  type 
have  their  bottoms  planed.  If  the  bottom  is  not  to  be 
planed,  it  should  be  left  as  nearly  parallel  with  the  center 
line  dd  as  possible.  After  having  adjusted  the  centers  of 
the  guides  and  the  jaws  so  that  they  all  come  level,  and  so 
that  there  is  sufficient  stock  for  finishing  these  parts,  a sur- 
face gauge  is  set  to  the  height  of  the  center  of  the  guides, 


60 


BENCH,  VISE,  AND  FLOOR  WORK.  § 21 


and  the  line  dd  is  drawn  on  painted  strips  or  spots  on  both 
sides  and  ends  of  thecasting.  If  the  bottom  is  to  be  planed, 
the  line  /'/'should  be  drawn  parallel  to  dd,  and  at  the  proper 
distance  from  it.  After  this,  the  blocks  r,  r at  the  ends  of 
the  guides  are  removed,  and  a line  (either  a piece  of  piano 
wire  or  a sea-grass  fish  line)  is  stretched  through  the  guides 
along  the  line  ee.  The  distance  from  this  line  ee  to  the 
center  of  the  crank-shaft  bearing  is  measured,  and  the  line  gg 
established  and  marked  off  on  the  jaws  of  the  bearing.  Then 
the  distances  h , h are  determined,  and  the  lines  i i and  i'  i 
drawn  so  as  to  determine  the  amount  of  stock  to  be  removed 
from  each  end  of  the  bearing. 

The  height  of  the  governor  pad  from  the  bottom  of  the 
bedplate  is  marked  off  at /,  and  the  amount  to  be  removed 
from  the  rocker-arm  hub  is  laid  off  at  k.  After  this,  the 
( end  of  the  bed  to  which  the  cylinder  is  to  be  bolted  is  also 
laid  off,  the  line  m n being  drawn,  thus  determining  the 
amount  to  be  faced  from  this  end.  The  distance  from  the 
end  of  this  face  to  the  center  of  the  bearing  should  agree 
with  the  drawing.  It  will  next  be  necessary  to  machine 
most  of  the  faces  already  determined,  after  which  the 
lines  o p,  s t,  and  o t may  be  laid  off  on  the  jaws  of  the  bear- 
ing, and  the  center  of  the  rocker-shaft  hub  at  k may  be  laid 
off  the  proper  distance  below  the  center  line.  After  the 
guides  are  bored  and  the  end  faced  off  to  the  line  m n , the 
bolt  circle  may  be  drawn  on  this  end,  and  the  bolt  holes  laid 
out  in  a manner  similar  to  that  described  for  the  laying  out 
of  bolts  and  flanges,  Art.  80. 

If  the  laying  out  is  done  on  a table  having  lines  running 
both  lengthwise  a.nd  crosswise,  it  will  simplify  matters  to 
adjust  the  bed  so  that  some  one  line  corresponds  with  the 
center  line  d d-,  after  which  many  of  the  measurements  may 
be  obtained  from  the  other  lines. 

85.  Gauges  for  Laying  Out  Key  Seats.  — Differ- 
ent types  of  gauges  have  been  adopted  for  laying  out  key 
seats,  but  for  the  ordinary  run  of  work  the  form  shown  in 
Fig.  57  will  be  found  very  useful.  This  consists  of  a ring 


§ 21  BENCH,  VISE,  AND  FLOOR  WORK. 


61 


of  cast  iron  a that  is  bored  to  the  correct  diameter  b,  and 
that  has  the  necessary  keyways  laid  out  in 
it,  as  shown  at  c and  d.  This  ring  may 
be  slipped  over  the  shaft,  and  the  keyways 
marked  from  it;  it  may  then  be  removed 
and  placed  on  a hub  of  the  crank  or 
wheel,  and  the  keyways  on  it  also  marked 
out,  thus  insuring  the  accurate  location 
of  these  keyways.  fig.  57. 

86,  Faying  Out  Ends  for  Small  Rods. — A conve- 
nient method  of  laying  out  the  ends  of  small  rods  is  shown 
in  Fig.  58.  In  this,  the  piston  rod  a is  placed  on  V blocks 
that  bring  it  level.  A stake  or  post  b is  put  into  a hole  in 
the  plate  or  table,  to  which  it  has  been  fitted,  so  that  it 
stands  perpendicular,  as  shown,  with  its  upper  end  through 


the  holes  in  the  fork  c , fitting  it  accurately.  The  top  end  of 
the  post  b has  a small  center-punch  mark  in  it,  which  pro- 
vides a convenient  center  from  which  to  draw  the  circle  d 
for  the  rounded  end  of  the  fork.  The  parallel  edge  lines 
from  e and  e tangent  to  this  circle  are  drawn  by  means  of  a 
surface  gauge,  after  the  fork  has  been  revolved  to  a vertical 
position  and  set  to  a square. 


C.  S.  III.— 17 


■ 


ERECTING. 

(PART  1.) 


FLOOR  WORK. 


BLOCKING. 


INTRODUCTION. 

1.  Definition. — The  term  blocking ds  applied  to  the 
various  pieces  of  material  that  are  employed  for  temporarily 
supporting  work  that  is  being  done  on  the  erecting  floor  or 
in  the  field.  The  purpose  of  the  temporary  supports  is  either 
the  alining  of  the  work  in  some  particular  direction  or  direc- 
tions, or  the  raising  of  the  work  above  a certain  position  in 
order  to  make  it  more  accessible. 

2.  The  form  of  the  blocking  depends  on  the  character 
of  the  work  for  which  it  is  to  be  used  and  the  service  it  is 
intended  to  perform.  In  a great  many  cases  the  simplest 
form  and  the  most  elaborate  form  of  blocking  can  be  and 
are  advantageously  used  alongside  of  each  other  on  the 
same  piece  of  work. 

3.  The  simpler  forms  of  blocking  merely  serve  to  sup- 
port the  work;  while  the  more  elaborate  forms  can,  in  ad- 
dition, be  employed  for  moving  the  work  to  an  extent 
depending  on  their  construction.  Among  the  simpler  forms 
of  blocking  may  be  mentioned  wooden  blocks , trestles , and 
iron  parallel  blocks.  Trestles  are  known  by  the  name  of 
horses  in  many  localities.  Screzv  jacks  and  stone  jacks  are 

§22 


For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


ERECTING. 


§22 


examples  of  the  more  elaborate  forms  of  blocking,  and 
hydraulic  jacks  are  often  used  for  lifting  work,  but  not  for 
blocking  or  holding  it. 


WOOD  BLOCKING. 

4.  Wooden  Blocks.  — For  supporting  the  heavier 
classes  of  work,  either  on  the  erecting  floor  or  in  the  field, 
wooden  blocks  are  extensively  used.  The  blocks  are  gen- 
erally made  square;  they  may  have  a thickness  that  varies 
from  2 to  14  inches,  and  a length  that  varies  from  2 to  6 feet 
or  more.  Pine  and  similar  soft  woods  are  often  used  for 
blocking,  on  account  of  their  low  price;  there  is  no  partic- 
ular objection  to  the  use  of  the  softer  woods  for  work  done 
away  from  the  shop,  where  the  chances  are  that  the  blocking 
will  not  be  in  use  for  any  great  length  of  time.  Hard  wood 
is  preferable  for  work  on  the  erecting  floor,  since  it  will 
keep  its  shape  better  and  last  much  longer  than  the  softer 
woods. 

5.  Wooden  blocks  are  sometimes  used  for  packing  blocks 
that  are  to  be  placed  under  the  clamps  that  secure  work  to 
the  table  of  a machine  tool.  When  used  for  this  purpose, 
it  is  recommended  that  hard  wood  which  has  been  sawed 
square  across  the  grain  be  used.  The  block  should  then  be 
placed  on  end  so  that  the  grain  is  at  right  angles  to  the 

table,  on  account  of  the  fact 
that  wood  is  less  easily  com- 
pressed in  the  direction  of  its 
length  than  across  the  grain. 

6.  Trestles. — The  trestle 
is  used  as  a support  for  large, 
but  comparatively  light,  work. 
It  may  be  made  as  is  shown 
in  Fig.  1.  The  legs  should  be 
cut  so  as  to  leave  a shoulder  a , 
and  should  be  bolted  to  the  beam  b by  bolts  passing  through 
the  legs  and  the  beam.  Lagscrews  are  often  used  instead 


22 


ERECTING. 


3 


of  through  bolts,  but  their  use  for  this  purpose  is  not  recom- 
mended. When  great  stiffness  is  desired,  or  when  the 
weight  to  be  supported  is  rather  heavy,  the  legs  may  be  tied 
together  near  the  bottom  by  boards  nailed  across  them. 
The  only  objection  to  this  is  that  the  trestles  then  cannot  be 
stacked  on  top  of  one  another  when  not  in  use.  Trestles 
may  be  made  of  any  convenient  size;  when  they  are  used 
frequently  they  should  be  constructed  of  hard  wood. 


IRON  BLOCKING. 

7.  Rectangular  Iron  Blocking. — The  simplest  and 
the  most  common  forms  of  iron  blocking  are  the  solid  par- 
allel bars  used  in  connection  with  machine  tools.  Large 
parallel  bars,  or  parallel  blocks,  as  they  are  often  called, 
are  usually  made  hollow,  and  are  then  well  ribbed  in  order 
to  safely  carry  the  great  weight  often  placed  upon  them. 

8.  Two  excellent  styles  of  parallel  blocks  are  shown  in 
Figs.  2 and  3.  The  block  shown  in  Fig.  2 has  a form  that 
combines  considerable  strength  with 

lightness.  It  is  planed  all  over  so  that  „ F , JL 

opposite  sides  are  parallel  and  adjacent  

sides  are  at  right  angles.  When  a 
number  of  such  blocks  are  made,  it  is 
advisable  to  make  their  corresponding 

dimensions  equal,  in  order  that  the  G 

blocks  may  be  used  in  pairs.  The 

block  shown  in  Fig.  2 is  so  constructed 

that  a number  of  equal  blocks  may  be 

piled  up  to  suit  the  requirements  of 

the  work  and  then  form  practically  a 

single  block.  Holes  for  dowel-pins  are 

drilled  in  corresponding  positions  in  the  four  faces  of  each 
block.  The  dowel-pins  are  made  a good  fit;  they  prevent 
the  blocks  from  slipping  on  each  other  and  at  the  same  time 
permit  them  to  be  readily  separated.  One  of  the  dowel-pins 
is  shown  at  a. 


Jr 


4 


ERECTING. 


22 


9.  The  block  shown  in  Fig.  3 has  the  general  form  of  a 
box;  it  is  finished  all  over  and  is  provided  with  T slots  and 
V grooves,  as  shown..  The  V grooves  in  the  sides  permit 
the  block  to  be  used  with  either  side  up  for  round  work;  the 


Fig.  3 


T slots  permit  the  work  to  be  fastened  to  the  block,  or  the 
block  to  be  fastened  in  position  by  bolfs.  Blocks  of  this  type 
may  be  used  singly,  or  they  may  be  piled  up  to  any  height 
that  the  work  may  require. 

1 0.  When  making  cast-iron  parallel  blocks,  it  is  recom- 
mended that  they  be  made  in  sets,  in  which  all  the  blocks 
that  are  used  together  are  exact  duplicates.  Blocks  of  dif- 
ferent sizes  may  be  made  with  a rectangular  cross-section 
and  with  the  short  side  of  the  large  block  equal  to  the  long 
side  of  the  next  smaller  size,  and  the  long  side  of  each  from 
two  to  three  times  as  long  as  the  short  side. 

11.  Cylindrical  Iron  Blocking. — A kind  of  blocking 

that  is  quite  convenient  for  some  classes  of  work,  together 
with  its  application  to  a piece  of  work,  is  shown  in  Fig.  4. 
The  blocking  greatly  resembles  a short  section  of  flanged 
cast-iron  pipe;  the  sections  may  have  the  flanges  strength- 
ened by  ribs,  as,  for  instance,  the  sections  a , a\  or,  the 
flanges  may  be  plain,  as  those  of  the  sections  b,  b.  The 
flanges  should  be  faced  straight  and  parallel  with  each 
other,  and  the  different  sections  should  all  have  the  same 
length. 


22 


ERECTING. 


5 


12.  A lighter  form  of  pipe  blocking  is  made  of  wrought 
iron  or  steel  pipe  that  is  threaded  at  both  ends  to  receive 
flanges.  The  latter  should  be  faced  after  they  are  screwed 
on  the  pipe. 


13.  Adjustable  Parallel  Blocks.  — The  adjustable 
parallel  block  is  illustrated  in  Fig.  5 (a).  Its  first  cost  is 
greater  than  that  of  ordinary  parallel  blocks,  but  it  will  be 
found  both  a time-saving  and  money-saving  device  on  ac- 
count of  the  fact  that  one  adjustable  parallel  block  displaces 
a number  of  the  ordinary  non-ad justable  type.  By  far  the 
greatest  advantage  of  the  adjustable  parallel  block  lies  in 
the  fact  that  any  thickness  within  the  range  of  the  block 
can  be  obtained.  In  other  words,  it  can  be  adjusted  exactly 


6 


ERECTING. 


§22 


to  the  requirements  in  any  particular  case.  It  consists  of 
two  separate  pieces  a and  b that  are  movably  connected  to- 
gether by  a dovetail,  which  is  clearly  shown  in  the  end  view. 
After  the  two  pieces  have  been  carefully  fitted  together,  the 


a 

a 

iT 

b 

-fch 

b 

JVWWWWVVV| 


0» 

Fig.  5. 


block  is  planed  so  that  its  surfaces  are  square  with  one  an- 
other, and  opposite  surfaces  are  parallel.  The  dovetailed 
slide  being  at  an  angle  to  the  surfaces  a'  and  b\  the  distances 
between  these  two  surfaces  may  be  varied  by  sliding  the 
pieces  upon  each  other.  In  order  that  the  pieces  may  not 
slide  under  a heavy  load,  the  inclination  of  the  slide  to  the 
surfaces  a'  and  b'  should  not  exceed  10°. 


14.  An  adjustable  parallel  block  constructed  as  shown 
in  Fig.  5 (a)  may  be  made  any  convenient  size  and  will  be 
found  a very  useful  appliance  for  the  various  machine  tools. 
The  block  may  be,  and  often  is,  used  as  a gauge  by  which 
to  set  a planer  tool  for  planing  work  to  an  exact  height 
above  the  planer  or  shaper  table. 

15.  If  the  base  b is  extended  to  two  and  one-half  times 
its  ordinary  length,  as  shown  in  Fig.  5 ( b ),  and  rack  teeth 
are  cut  the  whole  length  of  a good  gauge  for  getting  the 
exact  thickness  of  the  racks  used  for  various  machine  tools 
is  obtained.  The  teeth  in  the  part  a are  placed  in  mesh 
with  the  pinion  and  the  part  b is  set  so  as  to  give  just  the 
right  fit  between  the  pinion  and  the  rack  seat.  After  the 
gauge  is  set,  it  may  be  removed;  the  pieces  of  rack,  which 


ERECTING. 


7 


§ 22 

are  generally  left  too  thick,  are  now  finished  to  the  size  in- 
dicated by  the  gauge.  The  pitch  of  the  teeth  cut  in  this 
gauge  must,  of  course,  be  the  same  in  every  case  as  that  of 
the  pinion. 


JACK-SCREWS  AND  HYDRAULIC  JACKS. 

16.  Jacks. — In  addition  to  the  parallel  blocks  just  de- 
scribed, the  lifting  device  known  as  a jack  is  almost  indis- 
pensable in  all  kinds  of  floor  work,  especially  in  erecting. 
Jacks  are  made  in  a large  variety  of  styles  and  sizes,  from 
those  intended  for  leveling  up  light  work  on  the  tables  of 
machine  tools,  to  the  heavy  jack-screws  and  hydraulic  jacks 
capable  of  raising  or  supporting  150  tons  or  more,  and  con- 
sequently are  used  for  a wide  range  of  work. 

17.  Simple  Leveling;  Jack. — The  simplest  form  of 
jack  consists  of  a circular  cast-iron  foot,  which  is  faced  at 
the  bottom  and  has  a tapped  hole  through 
it.  A square-headed  screw  with  a slightly 
rounded  top,  as  shown  in  Fig.  6,  is  used 
for  raising  the  work.  This  style  of  a 
jack-screw  is  used  principally  in  leveling 
up  work  on  the  tables  of  machine  tools, 
although  it  will  be  seen  later  that  jacks 
resembling  this  are  sometimes  made  in 
large  sizes  and  used  in  erecting. 

18.  Adjustable-Top  Leveling 
Jacks. — A good  little  case-hardened 
jack,  with  an  adjustable  cap,  which  is 
very  serviceable  for  machine-tool  work 
and  light  assembling,  is  shown  in 
Fig.  7 (a).  The  body  a is  tapped  to  re- 
ceive the  adjusting  screw  b , which  has  a 
square  top  and  holes  for  the  rod  c.  The 
cap  d is  attached  to  the  screw  by  a ball- 
and-socket  joint,  so  as  to  permit  the  cap  to  accommodate 
itself  to  the  angle  of  the  work.  When  a solid  or  conical  top 


8 


ERECTING. 


§22 


is  more  suitable  for  the  work,  a second  screw  ^is  substituted 
for  b.  The  foot  of  the  body  a is  counterbored  to  fit  the 


(a)  (b) 

Fig.  7. 


projection  on  the  auxiliary  base  f,  which  may  be  placed 
under  the  jack  when  a greater  height  is  required.  Auxiliary 
bases  of  different  heights  may  be  used  as  needed.  A special 
base  g is  also  furnished  with  the  jack  and  is 
used  where  this  form  of  base  is  more  suitable. 


19.  Another  very  serviceable  jack  for 
light  erecting  and  for  setting  work  on  ma- 
chine-tool tables  is  shown  in  Fig.  7 ( b ).  A 
steel  screw  a having  a square  thread  is  screwed 

/A 


*7?  >5 guare r* 

(a) 


Fig.  8. 


Fig.  9. 


into  a cast-iron  base  b , the  bottom  of  which  is  faced.  A 
cap  c is  attached  to  the  screw  by  means  of  a ball-and-socket 


§22 


ERECTING. 


9 


joint.  This  jack  serves  the  same  purpose  as  the  one  shown 
in  Fig.  7 (<?),  and,  like  that  jack,  is  useful  for  work  having 
the  surface  that  is  to  be  supported  at  a slight  inclination  to 
the  supporting  surface. 

20.  Sectional  Jack.  — A jack-screw  that  embodies 
some  good  features  is  shown  in  Fig.  8.  The  body  is  made 
up  in  sections,  as  shown,  and  has  a base  a that  can  be  used 
with  one  or  all  of  the  sections.  A removable  cap  which 
is  hollowed  out  on  the  lower  side  so  as  to  fit  the  rounded 
head  of  the  screw  and  which  has  a V groove  cut  into  the 
upper  side,  is  a great  convenience  for  some  classes  of  work. 
This  jack,  as  found  on  the  market,  may,  with  its  various 
bases,  be  adjusted  in  height  from  about  1^-  to  6 inches. 

21.  Laying-Out  Jack. — A jack  that  has  been  found 
very  serviceable  in  laying  out  is  shown  in  Fig.  9 (a).  A 
screw  with  a square  head,  which  is  rounded  at  the  top,  is 
screwed  into  a square  cast-iron  body.  The  body  may  be 
cored  out  as  shown,  in  order  to  lighten  the  jack. 

22.  Simple  Erecting  Jacks. — Fig.  9 (b)  illustrates  a 
simple  and  serviceable  erecting  jack  that  can  be  made  at 


very  small  cost.  These  jacks  are  low,  yet  have  enough  ad- 
justment for  a great  deal  of  ordinary  erecting  work.  An- 
other jack  of  the  same  class,  and  used  for  the  same  kind  of 


10 


ERECTING. 


§22 


work,  is  shown  in  Fig.  10.  It  is  made  strong  and  rigid  in 
order  to  serve  for  heavy  work,  and  has  a large  base,  which 
is  a very  great  advantage  either  upon  earth  floors  or  where 
the  floor  is  not  perfectly  rigid. 

23.  A great  deal  of  time  may  be  saved  by  using  jacks, 
as  they  can  be  adjusted  more  quickly  and  more  accurately 
than  the  same  adjustment  could  be  made  with  blocks  and 
wedges.  Any  number  of  jacks  permitted  and  required  by 
circumstances  may  be  used  at  different  points  of  a heavy 
part  in  order  to  support  it  properly. 

24.  Heavy  Erecting  Jack.  — The  jack  shown  in 
Fig.  11  may  be  used  for  work  that  is  excessively  heavy  and 

where  there  is  much  vibration. 
The  screw  is  made  with  a square 
thread  and  has  a cap  a mounted 
on  a spherical  head.  The  screw 
is  turned  by  means  of  a round  bar 
inserted  in  the  holes  in  the  en- 
larged part  b.  The  foot  c of  the 
jack  is  made  heavy  and  stiff. 
The  upper  part  of  the  foot,  that 
is,  the  threaded  portion,  is  slotted 
as  shown  at  d , so  that  when  the 
screw  has  been  adjusted  to  the 
proper  height  it  may  be  clamped 
by  means  of  the  bolt  e,  thus  pre- 
venting any  rotation  of  the  screw 
while  the  work  is  being  done. 

25.  Lifting  Jacks. — When  jacks  are  required  for  the 
purpose  of  lifting,  a different  design  with  a greater  screw 
travel  becomes  necessary.  Fig.  12  is  an  illustration  of  a 
jack  of  this  class.  The  head  of  the  screw  is  made  with  a 
cast-iron  cap  a that  rests  on  a solid  collar  b;  the  upper  end 
of  the  screw  is  turned  down  to  pass  through  the  cap  and 
is  beaded  over  to  prevent  the  cap  from  coming  off.  A 
round  bar  inserted  in  the  holes  at  b is  used  to  turn  the 


screw. 


§22 


ERECTING. 


11 


It  will  be  seen  that  this  jack  cannot  be  used  with  a 
straight  handle  in  places  where  the  screw  cannot  be  turned 
through  an  angle  of  at  least  90°  at  each 
setting  of  the  bar.  By  bending  one  end  of 
the  bar  through  an  angle  of  22|°,  and  in- 
serting the  bent  and  straight  ends  alter- 
nately, the  angle  through  which  the  screw 
turns  for  each  insertion  of  the  bar  is  greatly 
reduced.  It  is  thus  made  possible  to  operate 
the  jack  in  a comparatively  narrow  space, 
but  the  amount  of  time  required  for  the 
constant  resetting  of  the  bar  is  so  great 
that  this  method  becomes  objectionable 
where  much  work  of  this  kind  is  to  be  done. 

A jack  fitted  with  a reversible  ratchet  for 
operating  the  screw  is  preferable  in  most 
cases,  since  a great  deal  of  time  and  hard 
work  is  saved  by  its  use,  as  the  handle  of  the 
ratchet  can  be  turned  back  more  easily  and 
in  much  less  time  than  a bar  can  be  taken 
out,  turned  end  for  end,  and  again  inserted.  With  a properly 
formed  ratchet,  the  jack  can  be  operated  in  a very  much 
smaller  space  than  one  operated  by  a de- 
tachable bar. 

26.  Track  and  Stone  Jacks. — 

When  erecting  work  in  a shop  where  the 
facilities  for  handling  are  not  good,  and 
also  for  handling  it  upon  the  final  site, 
track  jacks  and  stone  jacks  are  very 
often  used,  on  account  of  their  great  con- 
venience. Fig.  13  illustrates  a stone  jack 
regularly  made  to  lift  12  tons  through  a 
height  of  about  20  inches.  The  load  is 
carried  either  on  the  head  a or  on  the  toe  b. 
The  work  is  raised  by  turning  the  handle  c 
about  its  center,  thus  turning  a train  of 
reducing  gears  that  engage  with  the 


fig.  12. 


12 


ERECTING. 


22 


rack  d.  The  track  jack  embodies  the  same  principles  as  the 
stone  jack,  but  is  operated  by  a lever  instead  of  a gear- 
train. 

27.  Hydraulic  Jacks. — Hydraulic  jacks  of  different 
kinds  are  used  very  largely  in  well-equipped  machine  shops. 
A hydraulic  jack  has  a plunger  that  operates  in  a cylinder 
into  which  water,  alcohol,  or  oil  is  pumped.  When  hydraulic 
jacks  are  subjected  to  cold  temperatures,  alcohol  must  be 
used,  on  account  of  its  resistance  to  freezing.  The  lifting 
is  done  by  the  pressure  of  the  fluid  in  the  cylinder.  A small 
hand  force  pump  is  contained  in  the  body  of  the  jacks,  by 


which  the  necessary  pressure  is  obtained.  Fig.  14  (a)  shows 
a hydraulic  jack  in  which  the  cylinder  a is  a part  of  the 
foot  b , while  the  head  c is  attached  to  the  plunger  d.  The 
pump  mechanism,  which  is  enclosed  in  the  head,  is  operated 
by  the  handle  e. 

28.  Fig.  14  (b)  illustrates  a hydraulic  jack  in  which  the 
plunger  g is  attached  to  the  foot  //,  and  the  cylinder  i is 
attached  to  the  head.  The  pump  mechanism  is  practically 
the  same  as  in  Fig.  14  ( a ).  The  arrangement  shown  in 
Fig.  14  (b)  permits  a lifting  toe  j to  be  cast  on  the  lower  end 
of  the  cylinder,  thus  making  it  possible  to  secure  a low 


22 


ERECTING. 


13 


hold,  which  is  not  possible  with  the  arrangement  shown  in 
Fig.  14  (a). 

29.  Hydraulic  jacks  range  in  capacity  from  3 to  150  tons ; 
the  larger  sizes  are  sometimes  used  as  hydraulic  presses  by 
attaching  them  to  the  work  by  means  of  suitable  bars.  In 
such  a case,  a convenient  portable  press  is  obtained  that  is 
suitable  for  work  that  cannot  be  taken  to  a stationary  press. 


MACHINE  FOUNDATIONS. 

30.  Introduction. — The  erecting  of  a machine  is 
usually  understood  as  including  both  the  erecting  in  the 
shop  in  which  it  is  made  and  the  erecting  upon  the  final 
foundation.  The  two  differ  principally  in  the  amount  of 
fitting  and  adjusting  that  is  to  be  done  and  the  facilities  for 
handling  the  heavier  parts.  The  fitting  and  the  adjusting 
of  all  the  parts  are  done  in  the  shop,  except  in  cases  where 
some  of  the  parts  are  dependent  on  the  foundation,  or  must 
be  fitted  to  other  parts  that  are  not  available  in  the  shop. 

31  e The  machine  should  in  all  cases  be  made  as  com- 
plete and  as  perfect  as  possible  before  it  leaves  the  shop, 
since  the  entire  equipment  of  the  shop  is  available,  and  the 
work  can  be  done  to  better  advantage.  Any  fitting  that  is 
necessary  while  setting  up  the  machine  upon  its  final  foun- 
dation must  be  done  with  a few  light  tools  that  can  easily  be 
shipped,  and  with  such  makeshift  devices  as  the  workman 
may  be  able  to  make.  His  ingenuity  is  often  severely 
tested,  and  the  most  skilful  workman  frequently  finds  it 
impossible  to  produce  the  grade  of  work  that  could  easily, 
and  at  a much  smaller  cost,  be  produced  in  the  shop.  It  is 
therefore  a matter  of  economy  to  be  sure  that  every  part  is 
properly  fitted  and  the  entire  machine  as  complete  as  pos- 
sible before  it  is  shipped.  The  erecting  on  the  final  founda- 
tion should  consist  simply  of  putting  the  parts  together  and 
making  the  final  adjustments.  This  is,  at  best,  not  an  easy 
task,  especially  when  the  machine  is  heavy,  as  the  facilities 


14  ERECTING.  § 22 

for  handling  are  almost  invariably  temporary  makeshift 
devices  that  operate  slowly. 

32.  Permanent  Foundation  and  Foundation- 
Iiolt  Templet. — The  permanent  foundation  is  usually  built 
up  of  concrete,  brick,  or  stone.  In  . building  the  foundation, 
due  provision  must  be  made  for  the  foundation  bolts.  Some- 
times these  bolts  are  built  solidly  in  the  foundation,  while 
at  other  times  they  are  set  in  pipes  that  hold  the  concrete  or 
cement  while  it  hardens  yet  permit  the  bolts  to  be  adjusted 
or  removed  entirely,  if  that  should  be  necessary.  In  either 
case  the  bolts  must  be  carefully  set,  so  that  when  the  bed  of 
the  machine  is  lowered  in  place  they  will  meet  the  bolt 
holes.  It  is  usually  best  to  make  a wooden  templet  having 
the  exact  thickness  of  the  bed  parts,  with  holes  in  the  exact 
location  of  the  bolt  holes  in  the  bed  through  which  the  bolts 
pass.  It  will  be  seen  that  by  locating  such  a templet  care- 
fully where  the  machine  is  to  stand,  the  bolts  can  be  set  to 
the  proper  height  and  in  the  right  place;  the  foundation 
may  then  be  built  up  without  any  danger  of  a misfit. 


ERECTING  FLOORS. 

33.  Introduction. — The  erecting  in  the  shop  is  done 
on  a floor,  the  construction  of  which  depends  on  the  weight 
of  the  machines  and  the  condition  of  the  earth  on  which  it 
is  built.  When  the  earth  is  dry  and  hard,  or  there  is  a rock 
bottom  to  build  upon,  the  foundation  of  the  floor  may  be 
shallow;  on  the  other  hand,  when  the  earth  is  wet  or 
unstable,  a deep  and  solid  foundation  should  be  built  up. 
The  depth  of  the  floor  foundation  depends  on  the  weights  of 
the  heaviest  parts  that  are  liable  to  come  upon  it. 

34.  Erecting  floors  are  made  up  in  different  ways, 
depending  on  the  class  of  work  to  be  done;  that  is,  whether 
they  are  intended  for  permanent  use  for  one  class  of  work, 
or  for  a wide  range  of  work,  the  needs  of  which  cannot  well 
be  anticipated  and  for  which  changes  must  constantly  be 


22 


ERECTING. 


15 


made.  The  first  cost,  also,  in  many  cases,  becomes  an  im- 
portant factor,  and  determines  the  style  of  floor  used.  To 
meet  the  various  requirements,  the  following  kinds  of  floor 
are  made : earth,  wooden  plank , scantling , wooden  block , brick, 
concrete,  and  iron  plate . 

35.  Earth  Floors. — In  places  where  the  earth  is  of  a 
firm  and  solid  character  and  little  money  can  be  spent  for 
a floor,  the  earth  is  simply  leveled  and  packed  down  so  as 
to  make  a smooth,  hard  floor.  Sometimes  the  surface  is 
formed  of  a layer  of  iron  chips  from  1 to  4 inches  thick  that 
are  mixed  with  salt  or  other  material  that  will  cause  them 
to  rust.  When  they  are  well  packed,  the  surface  will  rust 
into  a solid  smooth  mass  and  then  form  a very  good  floor. 
Besides  being  cheap,  the  earth  floor  can  easily  be  dug  up 
to  form  a pit  to  enable  any  machine  parts  that  project 
below  the  floor  line  to  be  attached.  On  the  other  hand, 
there  is  always  more  or  less  loose  sand  upon  the  surface, 
which  is  liable  to  get  into  the  working  parts  of  a machine 
and  thus  cause  trouble. 

36.  Single-Plank  Floor. — A comparatively  inexpen- 
sive floor  consists  of  3-  or  4-inch  yellow-pine  planking,  laid 
across  joists  that  are  placed  close  together  and  are  well 
braced  or  bridged  sidewise.  The  planks  are  sometimes  cov- 
ered with  a diagonal  floor  of  f-inch  to  lf-inch  pine.  The 
spaces  between  the  timber  should  be  ventilated.  This  style 
of  floor  is,  however,  not  very  rigid,  and,  hence,  the  heaviest 
grades  of  work  require  something  more  solid. 

37.  Double-Plank  Floor. — A more  rigid  floor  than 
the  plank  floor  previously  mentioned  is  illustrated  in  Fig.  15. 
The  floor  is  built  up  of  2"  X 4"  pine  scantling  a,  a,  with 
a facing  of  from  f-inch  to  lf-inch  pine  boards  laid  diag- 
onally, as  shown.  The  scantlings  are  laid  upon  timbers  c,  c, 
which  are  laid  in  a concrete  bed.  The  thickness  of  the  con- 
crete depends  largely  on  the  condition  of  the  ground,  but  if 
it  is  of  a firm  grade,  14  inches  should  be  sufficient  for  all  or- 
dinary purposes.  The  bed  is  built  up  by  first  laying  a course 
of  coarse  stone,  as  shown  at  d , and  running  in  some  cement, 


C.  S.  III. — 18 


16 


ERECTING. 


§22 


then  following  with  successive  finer  grades  of  broken  stone, 
and  finishing  with  a very  fine  grade.  Air  spaces  e , e are  left 
between  the  timbers;  these  may  be  ventilated  by  means  of 
openings  through  the  walls  or  by  holes  bored  through  the 


Fig.  15. 


floors.  Many  persons  claim  that  this  precaution  should  be 
taken  with  all  wood  floors  to  prevent  rotting.  The  tim- 
bers c , c are  made  4 in.  X 4 in. , 4 in.  X 6 in. , or  6 in.  X 6 in. , 
depending  on  the  duty  for  which  it  is  intended.  When  the 
4//X6//  timber  is  used,  it  is  laid  on  its  flat  side.  The  distance 
between  the  timbers  should  not  be  much  greater  than  the 
thickness  of  the  concrete,  and  it  is  generally  thought  best  to 
limit  the  distance  to  the  thickness.  This  makes  an  excellent 
floor,  and,  by  some,  is  preferred  to  all  other  styles. 

38.  A very  good  floor  is  made  with  a base  of  tar  con- 
crete. The  ground,  after  leveling,  is  covered  to  a depth  of 
about  6 inches  with  a layer  of  sand  that  is  well  rolled  down. 
On  top  of  this,  6 inches  of  tar  concrete  is  placed;  the  con- 
crete is  composed  of  small  broken  stones  covered  thickly 
with  heated  tar,  and,  after  leveling,  is  rolled  with  a heavy 
roller.  Finally,  a layer  of  sand  mixed  with  considerable  tar 
and  some  asphalt  is  applied,  while  hot,  to  a depth  of  about 
1^  inches  and  after  it  is  rolled  down,  is  allowed  to  harden. 
When  hard,  a layer  of  3-inch  spruce  planking  is  placed  on 
top  of  the  asphalt,  and  1^-inch  dressed  maple  flooring  in 
strips  about  4 inches  wide  is  finally  nailed  crosswise  to  the 
spruce  planking.  The  maple  flooring  is  not  tongued  and 


§22 


ERECTING. 


17 


grooved.  It  will  be  observed  that  no  air  space  is  left  be- 
tween the  concrete  and  the  flooring  in  this  design,  and  that 
the  planking  is  laid  directly  upon  the  concrete.  One  prom- 
inent firm  states  that  they  have  not  experienced  any  trouble 
by  the  rotting  of  the  planking,  as  is  claimed  by  many  to 
occur  when  the  flooring  is  laid  directly  on  the  concrete.  The 
quality  of  the  timber  used  and  the  amount  of  dampness  in 
the  location  are  important  factors  to  be  considered  when 
deciding  upon  the  kind  of  floor  to  use.  A tar  concrete  floor 
is  rather  expensive,  but  very  solid. 

39.  Wooden-Block  Floor. — A substantial  floor  may 

be  made  of  sawed  wooden  blocks,  either  cedar,  pine,  or  oak, 
that  are  placed  on  top  of  a concrete  bed.  One  prominent 
firm  has  constructed  a wooden-block  floor  in  the  following 
manner:  After  leveling  the  ground,  a layer  of  cinders 

6 inches  thick  was  placed  on  the  ground  and  thoroughly 
rolled  down  with  a heavy  steam  roller.  A bed  of  concrete 
4 inches  thick  was  laid  on  top  of  the  cinders  and  thoroughly 
leveled.  The  blocks  were  6 in.  X 4 in.  X 4 in.,  sawed  from 
well-seasoned  oak;  their  ends  were  dipped  into  liquid  as- 
phalt, and  the  blocks  were  then  laid  directly  on  top  of  the 
concrete  bed. 

Another  firm  omits  the  cinders  and  places  the  concrete 
bed  directly  on  the  leveled  ground,  making  the  concrete  bed 
about  8 inches  thick.  The  blocks  are  cedar  wood  sawed  to 
3 in.  X 12  in.  X 5 in.  ; these  are  placed  end  to  end  and  butt- 
ing together  on  the  concrete,  so  that  their  height  is  5 inches. 
A space  of  \ inch  is  left  between  adjacent  rows,  which  is 
filled  with  a mortar  composed  of  1 part  of  Portland  cement 
to  2£  parts  of  sand. 

The  advantages  of  a wooden-block  floor  are  as  follows: 
(1)  It  is  easy  on  the  feet  of  the  workmen.  (2)  The  work  is 
not  so  liable  to  slip  on  it  as  on  other  kinds  of  floors.  (3) 
Cleats,  braces,  etc.  can  be  readily  attached  to  the  floor. 
(4)  The  expense  of  repairing  it  is  slight. 

40.  Brick  Floors  and  Concrete  Floors. — Occasion- 
ally, a floor  is  made  of  brick  laid  in  cement  and  placed  on 


18 


ERECTING. 


§22 


a solid  concrete  foundation.  Sometimes  hard  paving  bricks 
that  are  laid  on  edge  are  used  instead  of  ordinary  bricks, 
and  cement  is  run  in  between  them  to  fill  the  cracks.  In 
some  localities,  a concrete  base  is  covered  with  a thick 
layer  of  cement,  which  forms  a very  smooth  and  hard  floor 
that  is  impervious  to  moisture. 

41.  Cast-Iron  Plate  Floors.  — The  cast-iron  plate 
floor  is  perhaps  the  best  floor  for  large  work,  but  its  great 
expense  has  in  the  past  prevented  its  coming  into  general 
use.  It  is,  however,  adapted  to  so  many  uses  that,  in  many 
shops,  the  expense  is  warranted,  since  it  serves  as  a laying- 
out  table,  a machine-tool  foundation,  and  a machine-tool 
table,  and,  also,  as  an  erecting  floor.  In  large  shops, 
especially  where  there  is  a large  amount  of  work  that  is  too 
heavy  to  be  machined  in  the  stationary  machine  tools,  such 
a floor  provides  an  excellent  means  for  setting  up  the  heavy 
parts  and  doing  the  machining  with  portable  machine  tools, 
such  as  radial  drills,  traverse  head-shapers,  slotting  machines, 
special  milling  and  grinding  fixtures,  etc.,  which  may  be 
driven  by  means  of  ropes,  electric  motors,  or  compressed  air. 

42.  One  or  two  large  horizontal  boring  mills  maybe  set 
alongside  an  iron-plate  floor  in  such  a manner  that  the  floor 
forms  the  table  of  the  machines;  this  arrangement  has  been 
found  very  convenient  in  shops  where  much  boring  is  done 
on  large  pieces.  A planer  set  with  the  side  of  its  bed  against 
such  a floor  may  also  be  made  to  operate  on  a heavy  part 
fastened  upon  the  floor,  by  means  of  a special  head  bolted 
to  the  table. 

43.  The  top  of  the  floor  should  be  planed  true,  and 
should  be  provided  with  T slots  for  the  purpose  of  allowing 
the  work  or  portable  machines  to  be  bolted  to  it.  The  slots 
are  usually  made  at  right  angles  to  each  other,  although 
sometimes  they  are  all  made  parallel  to  one  side;  occasion- 
ally, when  much  circular  work  is  to  be  machined  upon  the 
floors,  the  slots  are  run  in  concentric  circles  with  radial  slots 
crossing  them  at  regular  intervals. 


ERECTING. 


§ 22 

4-1.  The  plates  are  generally  made  stiff  enough  to  allow 
them  to  be  supported  upon  masonry  columns  without  deflec- 
tion. This  greatly  facilitates  the  leveling  up  of  the  plates, 
when,  for  any  reason,  they  get  out  of  true.  Sometimes 
they  are  laid  in  a solid  bed  of  concrete.  The  plates  are  then 
supported  at  every  point,  and  when  the  foundation  is  heavy, 
and  the  plates  are  leveled  up  very  carefully  when  they  are 
first  set,  the  floor  is  quite  satisfactory  for  some  time;  but  if, 
for  any  reason,  the  foundation  should  yield  slightly,  or  the 
plates  should  not  be  set  quite  right  at  first,  it  is  impossible 
to  set  them  true  without  taking  up  the  whole  floor  and 
resetting  it  completely.  This  is  a very  expensive  piece  of 
work,  and,  for  this  reason,  the  masonry  supports  with  open- 
ings between  them  that  make  all  parts  below  the  floor  acces- 
sible are  generally  preferred.  Iron  plates  are  sometimes 
objected  to  because  they  are  cold  and  slippery,  but  after 
workmen  have  become  accustomed  to  an  iron  floor,  these 
objections  are  soon  forgotten. 


FLOOR  PITS. 

45.  Introduction. — It  is  often  necessary  in  erecting 
large  work  to  make  provision  for  parts  that  extend  below  the 
floor  line,  or  to  get  at  some  of  the  parts  from  beneath  the 
machine.  For  this  purpose,  pits  are  made  at  suitable  places 
in  the  floor.  These  pits  are  often  made  with  cast-iron  floors 
about  their  edges,  and  are  often  lined  with  plates  with 
T slots  running  down  at  intervals  on  the  inside.  Pits  are 
also  used  in  machining  very  large  pieces,  such  as  flywheels, 
that  are  too  large  to  be  machined  on  a boring  mill  or  in  a 
lathe. 

46.  The  construction  of  pits,  like  the  construction  of 
erecting  floors,  depends  very  largely  on  the  class  of  work 
done  in  the  shop.  When  a definite  line  of  manufacture  is 
carried  on,  a pit  suited  to  the  needs  of  the  work  can  be  built, 
but  where  work  of  a miscellaneous  character  is  done,  it  is 


20 


ERECTING. 


22 


impossible  to  anticipate  the  needs  that  may  arise  at  any 
time,  and  a pit  that  can  easily  be  enlarged  or  changed  will 
be  the  most  suitable. 


47.  Pit  Construction  for  a Definite  Dine  of 
Work. — Fig.  16  shows  a pit  that  is  built  for  the  purpose  of 
erecting  vertical  boring  mills.  The  sides  of  the  pit  a are 
built  up  of  brick  or  stone,  and  iron  plates  b , b are  placed  all 


around  the  mouth  of  it,  as  shown.  A convenient  size  of  pit 
for  this  class  of  work  is  made  about  4 feet  deep  by  4 feet 
wide;  the  length  depends  on  the  amount  of  work  to  be  done. 

48.  The  bed  of  the  machine  that  is  being  erected  is 
usually  mounted  upon  parallels  placed  across  the  pit,  as 
shown  in  the  illustration.  It  will  be  observed  that  two 
styles  of  machines  are  shown  in  Fig.  16.  The  machines  has 
the  housings  attached  to  the  sides  of  the  bed  at  d , and  the 
table  is  rotated  on  a spindle  that  extends  below  the  bottom 
of  the  bed.  The  lower  end  of  the  spindle  is  carried  in  a 
step  bearing  that  is  placed  in  a frame  which  is  bolted  to  the 


§22 


ERECTING. 


21 


bottom  of  the  bed.  In  order  to  fit  this  frame  properly,  it  is 
necessary  to  have  plenty  of  room  beneath  the  bed;  for  this 
reason,  the  bed  is  placed  upon  two  parallels  on  each  side. 
The  other  two  machines  shown  are  self-contained.  The 
housings  and  the  bed  are  one  casting,  and  the  spindle  of  the 
table  does  not  extend  below  the  bed.  In  this  case,  one  set 
of  parallels  is  sufficient  to  support  the  machine  during 
erection. 

49.  Fig.  16  incidentally  illustrates  several  styles  of  large 
parallel  bars.  The  bars  <?,  e,  which  are  made  of  cast  iron, 
have  the  general  form  of  a box  that  is  open  at  the  bottom 
and  is  subdivided  into  several  compartments  by  webs. 
These  webs  tie  the  tops  and  sides  together  and  greatly 
stiffen  the  bar.  The  object  of  making  the  bars  hollow  is  to 
reduce  their  weight.  It  is  an  advantage  to  have  all  the 
bars  in  a set  made  the  same  height,  since  three  or  more  can 
then  be  used  for  supporting  a large  piece  of  work  having  a 
plane  surface  at  the  bottom. 

The  parallel  bars  ft  f have  an  I section  and  are  strength- 
ened at  regular  intervals  by  ribs,  as,  for  instance,  by  the  one 
shown  at  f\  A large  parallel  bar,  as  the  bar  g,  for  instance, 
is  occasionally  made  with  a rectangular  hole  and  a T slot 
cored  in  it.  The  T slot  permits  work  to  be  attached  to  the 
bar  by  means  of  bolts  and  clamps. 

50.  Large  Masonry  Pit. — Fig.  17  shows  a large  ma- 
sonry pit  intended  for  large  and  heavy  work.  For  a given 
class  of  work,  such  a pit  should,  when  possible,  be  designed 
so  that  it  will  be  suitable,  especially  to  that  class  of  work. 
For  general  work,  a pit  must  be  designed  to  cover  as  broad  a 
range  of  work  as  possible.  A pit  about  40  feet  long,  12  feet 
wide,  and  20  feet  deep  is  a size  well  adapted  for  heavy 
work.  The  one  shown  in  Fig.  17  suggests  a design  that  is 
suitable  for  most  cases.  The  ends  a , a and  the  sides  b may 
be  built  up  of  stone,  while  the  bottom  c is  made  of  concrete 
and  faced  with  cement.  The  top  of  the  pit  is  surrounded 
with  cast-iron  plates  d,  d , provided  with  T slots,  the  plates 
being  planed  and  set  level.  The  ends  of  the  pit  may  be 


22  ERECTING.  § 22 

built  up  in  steps,  as  shown,  or  may  be  made  straight,  as 
indicated  by  the  dotted  lines  e. 

5 1 . When  the  pit  is  not  in  use,  it  is  covered  with  a 
plank  floor,  a section  of  which  is  shown  in  place  at  f.  The 
floor  is  supported  upon  I beams,  as  g,  which  are  set  in 
pockets  //,  h , in  the  sides  of  the  pit.  The  covering  floor  is 


Fig.  17. 


made  up  in  sections  so  that  it  can  easily  be  removed,  and 
each  section  is  provided  with  two  rings  i,  i to  facilitate  the 
handling.  The  rings  are  attached  with  staples  and  let  into 
the  plank,  so  that  when  they  are  not  in  use  they  lie  below 
the  surface  of  the  floor.  These  pits  may  be  made  with  one 


ERECTING. 


§ 22 


23 


or  more  sets  of  pockets  j,  j to  receive  the  I beams,  upon 
which  to  support  sections  of  the  floor  when  the  full  depth 
of  the  pit  is  not  required.  Such  a pit  may  be  used  either 
for  erecting  or  for  machining  large  parts,  as  described 
later. 

In  some  shops  it  is  preferred  not  to  floor  the  pit  over.  In 
such  a case  it  is  advisable  to  place  a stout  removable  hand 
railing  around  the  pit  to  prevent  workmen  from  stumbling 
into  it. 

52.  Another  style  of  pit,  which  has  the  advantage  of 
being  both  cheap  and  easily  changed  or  enlarged,  is  shown 
in  Fig.  18.  The  earth  is  simply  dug  away  where  the  pit  is 
to  go,  and  the  floor,  which  rests  upon  heavy  horizontal  tim- 


Fig.  18. 

bers  a , a is  supported  about  the  outside  of  the  pit  by  means 
of  vertical  timbers  b,  b standing  upon  blocks  c , c.  The 
floor,  which  covers  the  pit  when  it  is  not  in  use,  is  made  in 
sections  and  is  supported  by  timbers  that  are  set  into 
pockets  d , which  are  cut  into  the  side  timbers. 


24 


ERECTING 


§22 


Fig.  19. 


ERECTING. 


25 


22 


USE  OF  ERECTING  PIT, 

53.  Assembling  a Flywheel. — Large  flywheels,  rope 
wheels,  gear-wheels,  and  other  similar  wheels  are  usually 
assembled  in  the  erecting  pit.  The  assembling  and  machin- 
ing of  the  rim  of  a large  built-up  flywheel  is  an  excellent 
example  of  the  use  of  the  erecting  pit.  One  method  of  do- 
ing this  work  is  here  described.  Parallel  bars  a , a,  Fig.  19, 
are  bolted  opposite  each  other  to  the  plates  surrounding  the 
mouth  of  the  pit,  and  temporary  bearings  b , b that  will 
bring  the  center  of  the  shaft  c about  30  inches  above  the 
floor  level,  are  placed  on  top  of  the  parallel  bars  so  that  they 
are  fairly  in  line  with  each  other.  The  shaft  c with  the 
hub  d on  it  is  now  picked  up  by  a crane  and  lowered  into 
the  bearings,  which  are  properly  alined  to  suit  the  shaft. 
The  bearings,  which  do  not  need  any  caps,  are  now  bolted 
down  to  the  parallel  bars.  In  another  method  of  lining  the 
bearings,  the  shaft  is  blocked  up  until  it  is  level;  the  bear- 
ings, which  are  considerably  larger  than  the  journals,  are 
shifted  into  place  and  bolted  down,  and  Babbitt  metal  is 
poured  into  the  bearings  around  the  journals. 


54.  All  the  joint  faces  of  the  sections  of  the  rim  hav- 
ing been  properly  faced  prior  to  the  erection,  one  section 
is  picked  up  by  the  crane  and  gently  lowered  on  the  hub, 
to  which  it  is  fastened  while  in  a vertical  position  by  tem- 
porary bolts.  The  shaft  is  now  revolved  sufficiently  to  bring 
the  next  seat  of  the  hub  to  a horizontal  position,  and  after 
the  fastened  section  has  been  securely  blocked  to  prevent 
rotation  of  the  shaft,  another  section  is  lifted  into  place  and 
is  attached  to  the  hub  and  the  first  section.  This  operation 
is  repeated  until  the  wheel  has  been  assembled.  The  holes 
in  the  arms  and  hub  are  now  reamed  one  by  one  to  match 
exactly,  and  the  permanent  bolts  are  then  carefully  fitted, 
driven  home,  and  the  nuts  securely  screwed  up,  as  shown 
at  e,  e. 

55.  In  order  to  turn  the  sides  and  face  of  the  rim,  means 
must  be  provided  for  revolving  the  flywheel.  A common 


2G 


ERECTING. 


§22 


method  is  to  bolt  a large  annular  gear,  which,  for  conve- 
nience, is  made  in  short  sections,  to  the  arms  of  the  fly- 
wheel. One  of  these  sections  is  shown  at  f.  A pinion  g is 
then  placed  in  mesh  with  the  gear  and  is  driven  either  by  a 
rope  drive,  by  a belt  from  an  overhead  shaft,  by  an  electric 
motor,  by  a small  steam  engine,  or  by  a compressed-air  en- 
gine, as  is  most  convenient.  A heavy  bed  h is  then  bolted 
across  the  pit;  it  may  carry  two  slide  rests  i,  i,  in  order  to 
allow  both  sides  of  the  rim  to  be  finished  at  once. 

56.  If  the  flywheel  is  to  have  the  rim  polished,  a grind- 
ing rig  carrying  a suitable  emery  wheel  may  be  mounted  on 
the  carriage  i.  The  emery  wheel,  which  is  driven  in  any 
convenient  manner,  is  then  fed  slowly  across  the  surface 
that  is  to  be  ground  while  the  wheel  is  revolving  at  a suit- 
able speed. 

57.  Cutting  a Large  Spur  Gear. — Spur  gears  50  feet 
or  more  in  diameter  maybe  cut  in  the  following  manner: 
They  are  built  up  with  as  much  in  the  pit  as  will  bring  the 
center  of  the  shaft  within  as  convenient  a working  distance 
of  the  floor  as  possible.  The  spaces  between  the  teeth  are 
generally  cast  in  with  enough  allowance  to  insure  cleaning  up. 

58.  A rest  or  bed  similar  to  that  used  for  turning,  but 
carrying  a back-geared  milling  head  that  may  be  traversed 
the  whole  length  of  the  bed  is  placed  across  the  pit,  parallel 
with  the  shaft  that  carries  the  wheel.  The  bed  is  blocked 
up  until  the  axis  of  the  milling  spindle  and  the  axis  of  the 
wheel  shaft  are  at  the  same  height  above  the  floor.  The 
wheel  is  generally  erected  with  the  top  of  the  teeth  left 
rough;  these  may  be  finished  by  means  of  a milling  cutter 
fed  across  the  face  of  each  tooth  in  succession,  thus  bringing 
the  gear  blank  to  the  correct  outside  diameter.  The  pitch 
circle  is  next  laid  out  on  one  side  of  the  rim,  and  is  divided 
as  accurately  as  possible  by  means  of  a pair  of  dividers.  In 
order  to  insure  accurate  spacing  of  the  teeth,  it  is  well  to  go 
around  the  pitch  circle  with  a pair  of  trams,  using  as  long  a 
cord  as  possible,  and  then  subdivide  the  large  divisions  with 
dividers  The  thickness  of  the  teeth  on  the  pitch  circle  is 


ERECTING. 


27 


§22 

then  laid  off  and  all  points  of  division  are  carefully  marked 
with  fine  prick-punch  marks.  The  spacing  for  the  teeth  is 
then  obtained  by  making  the  division  marks  representing 
the  circular  pitch  successively  coincide  with  the  end  of  a 
stationary  pointer.  Suitable  clamps  will  have  to  be  pro- 
vided for  holding  the  wheel  still  while  the  cuts  are  taken. 

59.  A pair  of  end  mills  may  be  used  for  cutting  the 
tooth  spaces,  of  which  the  roughing  cutter  is  about  y1^  inch 
smaller  in  diameter  than  the  finishing  cutter.  The  section 
of  the  finishing  cutter  must  be  exactly  a duplicate  of  the 
profile  of  the  space  between  the  teeth.  The  roughing  cutter 
may  have  nicked  teeth,  but  the  finishing  cutter  should  be 
left  plain.  Both  cutters  can  advantageously  be  given  spiral 
cutting  edges. 

60.  The  cutting  of  large  gears  in  the  manner  just  ex- 
plained may  be  expedited  by  using  two  cutting  heads  for 
roughing  out  the  spaces  and  facing  the  end  of  the  teeth, 
placing  a cutting  head  at  each  side  of  the  wheel.  The 
finishing  should  be  done  by  one  head  entirely. 

61.  Assembling  a Large  Rope  Wheel. — Large  rope 
wheels  are  usually  built  up,  the  rim,  hubs,  and  arms  being 
separate  pieces.  The  rim  itself  in  many  cases  is  made  in 
segments.  The  following  description  shows  the  method 
that  is  in  vogue  in  one  prominent  shop  for  assembling  such 
a wheel,  the  wheel  whose  assembling  is  here  described  being 
25  feet  in  diameter  and  having  a face  7 feet  wide,  which 
contains  36  turned  grooves  for  lf-inch  rope.  The  wheel 
has  two  hubs  with  10  arms  for  each  hub;  the  rim  is  built  up 
out  of  10  segments  that  are  securely  bolted  to  one  another. 
The  arms  are  bolted  to  the  hubs  and  to  the  rim. 

62.  The  hubs  having  been  forced  on  the  shaft,  the  latter 
is  placed  in  temporary  bearings  placed  at  opposite  sides  of 
the  erecting  pit.  The  arms,  the  bolt  holes  in  the  ends  of 
which  have  been  previously  drilled  and  reamed,  are  now 
placed  in  position,  two  opposite  arms  on  each  hub  at  a time, 
and  are  supported  on  timbers  placed  across  the  pit.  They  are 


28 


ERECTING. 


§22 


then  attached  to  the  hubs  by  temporary  bolts,  and  the  holes 
in  the  hub  are  reamed  in  line  with  those  in  the  arms.  The 
permanent  bolts  are  now  fitted,  driven  home,  and  secured 
by  nuts.  All  the  arms  having  been  fastened,  the  sections 
of  the  rim  are  attached  one  by  one  until  the  wheel  is  com- 
pletely .assembled. 

63.  For  turning  the  grooves  for  the  ropes,  the  wheel  is 
driven  by  one  of  the  methods  explained  in  Art.  55.  A 
bed  that  carries  one  or  more  slide  rests  having  been  bolted 
across  the  pit,  the  face  of  the  wheel  is  turned  to  the  right 
diameter  and  the  position  of  the  grooves  is  then  laid  out. 
Square-nosed  tools  are  used  to  rough  out  the  grooves,  a wide 
one  being  employed  for  the  wide  part  of  the  groove  and 
narrow  ones  for  the  narrower  parts.  The  bottom  of  the 
groove  is  generally  made  round;  hence,  the  finishing  tool 
for  this  part  is  made  with  a round  nose  having  the  radius 
called  for  by  the  drawing.  Right-hand  and  left-hand  side 
tools  are  used  to  remove  the  remaining  stock  and  to  bring 
the  sides  of  the  grooves  to  the  correct  form  for  finishing. 
The  right-hand  side  tool  is  used  in  one  slide  rest  and  the 
left-hand  tool  in  the  other  slide  rest  in  order  to  prevent 
undue  thrust  in  one  direction,  as  would  result  if  two  tools 
cutting  in  the  same  direction  were  used  at  once.  The  finish- 
ing is  done  with  a formed  spring,  or  gooseneck  tool,  in  order 
to  have  the  finished  work  free  from  chatter  marks.  The 
sides  of  the  rim  are  turned  square  with  the  face,  and  any 
special  turning  that  may  be  specified  on  the  drawing  is  done. 

64.  The  wheel  should  be  rigidly  inspected  as  the  turn- 
ing progresses,  and  if  cracked  or  defective  castings  are 
found  in  the  rim,  they  should  be  replaced  before  the  wheel 
is  taken  down  for  shipment.  A defective  or  broken  segment 
may  have  a new  one  fitted  in  its  place,  and  the  new  seg- 
ment may  be  turned  without  great  loss  of  time  by  using  a 
reversing  countershaft  and  running  the  one  segment  back 
and  forth  past  the  tools  until  it  is  roughed  out  like  the  rest 
and  then  taking  a light  finishing  cut  over  the  whole  wheel. 
This  method  effects  a great  saving  on  a large  wheel  that 


ERECTING. 


29 


§ 22 

may  make  only  1 revolution  in  5 or  0 minutes.  The  work 
having  been  completed,  the  different  parts  are  plainly 
marked  to  show  which  way  they  go  together,  and  the  wheel 
is  then  taken  apart  for  shipment. 

65.  Using  Erecting  Pit  for  High  Work. — Vertical 
steam  engines  and  other  machines  that  are  too  high  to  be 
erected  on  the  erecting  floor  may  often  be  erected  on  the 
bottom  of  the  erecting  pit,  thus  gaining  the  extra  head- 
room  afforded  by  the  depth  of  the  pit. 


DRIVING  FITS,  PRESS  FITS,  AND  SHRINK 

FITS. 

66.  Introduction. — Two  pieces  of  work  may  be  joined 
together  by  creating  sufficient  friction  between  them  to 
prevent  separation  except  by  undue  means.  This  is  done 
in  practice  by  making  one  part  slightly  larger  than  the 
other  part,  and  placing  the  larger  part  into  the  smaller 
one,  or  placing  the  smaller  part  over  the  larger  one. 

67.  The  parts  that  are  to  be  joined  may  be  placed  to- 
gether either  by  pressing  or  driving  one  of  them  into  or 
over  the  other,  or  one  part  may  be  expanded  by  heating 
and  it  may  then  be  dropped  over  the  other  and  left  to  cool. 
Fits  that  are  made  by  driving  the  pieces  together  are  called 
driving  fits,  while  those  in  which  the  pieces  are  pressed 
together  are  called  press  fits. 

68.  When  one  piece  is  expanded  by  heating  and  is  then 
dropped  over  the  other,  it  tends  to  return  to  its  original 
size  in  cooling,  and  if  the  proper  allowance  has  been  made 
it  produces  a very  rigid  and  durable  joint.  This  is  called  a 
shrink  fit.  Shrink  fits  are  frequently  applied  in  making 
the  joints  of  flywheels,  strengthening  short  pipe  bends,  etc. 
In  all  these  cases  a link  or  bolt,  which  is  made  a little 
shorter  than  the  place  in  which  it  is  to  go,  is  heated  until  it 
goes  freely  into  place,  and  then  allowed  to  cool,  thus  draw- 
ing the  parts  tightly  together. 


30 


ERECTING. 


§ 22 


G£).  Either  the  driving  fits,  pressed  fits,  or  shrink  fits, 
when  properly  made,  produce  excellent  joints,  but  when  a 


shop  is  properly  fitted  up  with  presses,  and  the  character  of 
the  work  permits  it,  the  pressed  fit  is  preferred  by  many. 


ERECTING. 


31 


§ 22 


When  no  press  is  available,  the  parts  may  be  driven  together 
with  hammers  or  rams.  There  are,  however,  cases  where 
neither  a press  nor  a ram  can  be  applied,  and  the  shrink  fit 
may  be  used  to  the  best  advantage. 

70.  General  Construction  of  Hydraulic  Press. — 

Fig.  20  shows  one  style  of  a hydraulic  press  that  is  made  of 
200-,  300-,  and  400-ton  capacity,  and  is  used  for  such  work 
as  pressing  the  cranks  on  engine  crank-shafts  and  general 
pressing  on  or  off  in  making  press  fits.  The  tie-bars  a , a 
are  placed  on  either  side,  so  that  the  work  can  be  lowered 
into,  and  lifted  out  of,  the  press  with  a crane.  For  use  in 
railway  shops,  the  tie-bars  are  placed  one  below  the  floor 
and  the  other  overhead,  thus  enabling  the  rolling  in  and  out 
of  the  car  wheels  or  locomotive  wheels.  The  same  tie-rods, 
or  similar  ones,  may  be  used  with  hydraulic  jacks  for 
portable-press  work. 

71.  This  particular  machine  will  take  10  feet  between 
the  tie-bars  and  25  feet  between  the  ram  and  sliding  head. 
The  ram  b is  14  inches  in  diameter,  has  a stroke  of  4 feet, 
and  is  provided  with  a counterweight  so  that  it  returns  auto- 
matically when  the  release  valve  is  opened.  It  is  provided 
with  a safety  valve  that  can  be  set  to  open  at  a desired 
pressure  and  is  then  locked  up  in  a box  cast  on  the  cylinder, 
which  makes  it  impossible  to  push  more  than  a specified 
amount.  The  pressure  gauge  is  graduated  for  tons  pressure 
on  the  ram  and  pounds  per  square  inch  of  its  area.  The 
sliding  head  d moves  on  a track,  and  is  held  in  position  by 
steel  keys.  The  force  pump  is  driven  by  a belt  placed  on 
the  pulley  e,  and  takes  its  water  supply  from  a tank  under- 
neath, to  which  the  water  is  returned. 

72.  Portable  Press. — For  work  that  is  too  large  to  be 
placed  in  such  a machine,  a portable  form  may  be  used  that 
can  be  taken  to  the  work  and  can  be  made  to  conform  to 
its  varying  conditions.  If  the  portable  press  is  near  the 
stationary  press,  it  may  be  operated  by  connecting  it  to  the 
power-driven  pump  of  the  latter;  it  may  also  be  connected 
to  the  hydraulic  service  pipe  in  shops  provided  with  a 


C.  S.  III.— ip 


32 


ERECTING. 


§22 


hydraulic  service.  If  the  necessary  hydraulic  pressure  can- 
not be  obtained  in  either  one  of  these  ways,  the  press  may 
be  operated  by  a hand  force  pump. 

73.  All  shops  have  more  or  less  work  that  requires  to 
be  driven  or  pressed  together;  for  instance,  large  mandrels 
which  must  be  put  in  and  taken  out.  These  operations, 
which  often  require  the  help  of  several  men,  may  be  easily 
and  quickly  done  by  the  aid  of  a small  portable  press  like 


that  illustrated  in  Fig.  21.  This  press,  as  can  be  seen  by 
referring  to  the  illustration,  has  two  bars  1^  or  2 inches  in 
diameter  that  are  threaded  for  two-thirds  of  their  length  on 
one  end  and  enough  on  the  other  to  take  a nut.  Nuts  are 
screwed  on  at  intervals  to  form  stops  for  the  movable  head, 
and  two  supports  are  provided  for  a hydraulic  jack.  This 
tool  may  be  made  to  suit  the  needs  of  the  shop  in  which  it 
is  to  be  used,  and  any  ordinary  shop  jack,  not  exceeding  in 
power  the  strength  of  the  side  rods,  may  be  used  with  this 
device. 

74.  Press  Fits. — Press  fits  may  be  classed  under  two 
heads:  taper  fits  and  straight  fits.  If  a standard  1-inch 
cylindrical  plug-and-ring  gauge  be  tried  together  when  they 
are  at  equal  temperatures,  it  will  be  found  that  the  plug  can 
only  be  pushed  through  the  ring  by  exerting  considerable 
force.  The  reason  for  this  is  that  the  size  of  each  gauge  is 
so  near  that  of  the  other  as  to  make  the  fit  almost  perfect. 
If  a person  will  hold  the  ring  in  his  hand  for  5 minutes,  the 
ring  will  become  larger,  and  he  will  find  that  he  can  push 
the  plug  through  it  easily;  and  if  he  will  dip  the  plug  intQ 


§22 


ERECTING. 


33 


cold  water  and  warm  the  ring,  the  difference  in  size  be- 
comes so  great  that  the  plug  will  fall  through.  From  this 
experiment  it  is  seen  that  the  pressure  required  to  press  two 
parts  together  depends  on  the  difference  in  their  size. 

In  a press  fit,  the  internal  piece,  as  a shaft,  for  instance, 
must  be  enough  larger  than  the  hole  to  insure  the  develop- 
ment of  enough  friction  between  the  two  pieces  to  hold  it 
there  securely  when  pressed  home.  The  amount  of  friction 
is  judged  by  the  total  pressure  in  tons  on  the  piston  of  the 
hydraulic  press  that  is  required  to  press  the  pieces  together. 
The  allowance  that  has  to  be  made,  i.  e.,  the  difference  in 
the  diameter  of  the  two  pieces  that  is  required  in  order  to 
insure  a pressing  together  at  a given  pressure,  cannot  be 
calculated  with  any  degree  of  accuracy,  as  the  pressure 
depends  on  a number  of  variable  factors  whose  values  can- 
not be  determined,  even  approximately.  Some  of  these 
factors  are  the  length  of  the  hole  compared  with  its  diam- 
eter, the  relative  smoothness  and  truth  of  the  two  surfaces 
that  are  to  be  joined,  the  amount  of  metal  and  the  manner 
of  its  distribution  around  the  hole  of  the  external  piece,  and 
the  character  of  the  material.  For  this  reason,  experience, 
judgment,  and  experiment  must  be  relied  on;  in  order  to 
aid  the  judgment,  several  cases  taken  from  actual  practice 
are  here  given. 

75.  In  one  instance,  a car-wheel  seat  4J inches  in  diam- 
eter and  7 inches  long  required  30  tons  to  force  it  over  the 
axle,  an  allowance  of  .007  inch  having  been  made.  In 
another  case,  two  crankpins  were  required  to  go  in  holes 
5 in.  X 8 in.  at  50  tons  pressure.  A gauge  was  made  to  the 
diameter  of  the  holes,  and  another  one  was  made  .003  inch 
larger.  The  pins  were  turned  to  the  size  of  the  larger 
gauge,  and  went  home  at  a pressure  of  45  and  48  tons.  It 
is  the  practice  of  one  company  to  bore  the  hole  of  car  wheels 
4J  inches  in  diameter,  making  the  hole  cylindrical,  and  to 
turn  the  axle  a little  tapered,  just  enough  to  be  discernible 
to  the  calipers,  probably  .003  to  .005  inch;  the  holes  being 
5 inches  long,  the  wheels  go  home  under  a pressure  of 


34 


ERECTING. 


§22 


30  tons.  It  is  clear  that  where  such  a great  pressure  is 
required  to  force  the  pieces  together,  there  must  be  con- 
siderable wear  on  the  surface  of  both  parts  as  they  are 
being  pressed  together;  hence,  it  is  customary,  instead  of 
turning  the  internal  piece  cylindrical,  to  turn  it  with  a taper 
of  ToVo  °f  an  inch  to  the  inch  of  length  of  the  hole  to  be 
fitted.  If  the  hole  is  very  long,  less  allowance  may  be  made. 

70.  Taper  Press  Fits. — For  many  purposes,  the  taper 
fit  is  preferable  to  the  straight  fit.  In  a taper  fit,  the  hole  is 
bored  tapered,  generally  T!g-  inch  per  foot,  and  the  internal 
piece  is  turned  to  the  same  taper  as  the  hole,  or  in  the  prac- 
tice of  some,  an  increase  of  t-qVf  °f  an  inch  to  the  inch  of 
length  is  allowed;  that  is,  if  the  large  end  of  a hole  20  inches 
long  measures  15  inches,  the  large  end  of  the  internal  piece 
would  be  made  15.020  inches  in  diameter.  If  the  hole  is 
very  long,  the  amount  allowed  may  be  made  less. 

77.  Taper-pressed  fits  are  sometimes  made  in  the  fol- 
lowing manner:  The  hole  in  a hub,  wheel,  or  crank  is  first 
bored  with  a taper  of,  say,  -^g-inch  per  foot.  A hollow  cast- 
iron  plug  is  then  turned  or  ground  to  correspond  to  the 
hole  and  used  as  a sort  of  cylindrical  surface  plate  to  which 
the  inside  of  the  hole  is  scraped  until  it  is  true  and  round. 
The  pin  or  shaft  is  then  accurately  fitted  to  go  in  to  within 
a certain  distance  of  its  final  location,  generally  to  within 
from  1 to  4 inches.  The  following  illustration,  taken  from 
actual  practice,  serves  to  illustrate  the  manner  of  fitting  up 
this  class  of  work. 

An  engine  shaft  22  inches  in  diameter  carried  a hub  for  its 
flywheel  that  had  a bore  30  inches  long.  The  hole  in  the 
hub  was  scraped  so  that  the  hub  would  slide  to  within 
4^  inches  of  its  location,  and  was  pressed  in  the  remaining 
distance.  The  hole  in  the  crank  was  bored  18f  inches  and 
was  14  inches  long;  it  was  fitted  to  go  within  3|  inches  of 
the  shoulder  of  the  shaft  and  was  then  pressed  home.  The 
crankpin  had  a bearing  9§  inches  in  diameter  by  11  inches 
long  and  was  pressed  2£  inches.  In  all  these  cases  the 
shaft  or  pin  had  a taper  of  y1^  inch  per  foot. 


22 


ERECTING. 


35 


78.  Precautions. — Tables  have  been  made  by  the 
formulas  proposed  for  this  class  of  work  by  various  engi- 
neers, but  they  are  of  little  value  in  general  practice,  since 
only  experience  will  give  results  that  are  satisfactory.  How- 
ever, each  shop  can,  to  advantage,  make  useful  tables  from 
obtainable  data  and  their  own  experience.  It  is  better 
to  allow  a little  too  much  in  making  a forced  fit  than 
too  little,  for  if  the  internal  piece  is  too  tight,  it  may  be 
pressed  out  again  and  may  then  be  draw-filed  to  a smaller 
size. 

Before  putting  the  two  parts  together,  they  should  be 
thoroughly  lubricated  with  a heavy  oil  or  grease,  to  prevent 
cutting,  which  might  destroy  the  entire  fit  on  both  pieces. 
White  lead  is  often  used  instead  of  oil. 

79.  Allowances  for  Different  Fits. — The  amount 
allowed  on  various  kinds  of  work  for  fits,  such  as  running 
fits,  easy  driving  fits,  tight  driving  fits,  and  force  fits,  are 
treated  in  a general  way  in  the  following  articles  and  tables, 
which  represent  the  practice  of  several  good  shops  and  may 
be  taken  as  a general  average  of  allowances  made.  Varying 
conditions,  however,  may  call  for  different  allowances,  and 
hence  the  allowances  here  given  must  be  modified  to  suit  the 
requirements  of  the  work.  Running  fits  for  work  less  than 
1 inch  in  diameter  may  be  made  by  making  the  internal 
piece  .0015  to  .002  inch  under  the  size  of  the  hole,  while  a 
2^-inch  shaft  may  be  as  much  as  .003  under  size.  Driving 
fits  are  spoken  of  as  tight  and  easy.  A good  tight  driving 
fit  is  described  as  one-half,  and  a light  driving  fit  as  one- 
quarter,  of  the  force  fit. 

80.  The  following  table  of  diameters  and  allowances  for 
force  fits  represents  the  average  allowance  made  in  several 
good  shops;  but,  as  has  been  said  before,  the  conditions  pre- 
vailing in  the  work  being  done  govern  the  amount  of  force 
necessary  to  force  two  pieces  together.  For  this  reason 
the  pressure  necessary  to  push  the  parts  together  is  seldom 
given  with  a table  of  allowances. 


ERECTING. 


§ 22 


36 


TABLE  I. 


FORCE-FIT  ALLOWANCES. 


Diameter. 

Inches. 

Allowance. 

Inch. 

Diameter. 

Inches. 

Allowance. 

Inch. 

i 

.001 

12 

.012 

1 

.002 

14 

.014 

n 

.003 

16 

.015 

2 

.004 

18 

.016 

H 

.005 

20 

.018 

3 

.0055 

22 

.019 

4 

.007 

24 

.020 

5 

.008 

26 

.022 

6 

.009 

28 

.023 

8 

.010 

30 

.024 

10 

.011 

32 

.025 

81.  Shrink  Fits. — In  the  absence  of  a press  the  shrink- 
ing process  is  often  resorted  to,  but  in  general  it  is  not  as 
safe  or  satisfactory.  In  this  process  the  internal  piece  is 
made  larger  than  the  hole  it  is  to  go  into,  and  the  external 
piece  is  then  expanded  by  heat  to  allow  the  internal  piece 
to  be  easily  slipped  in. 

The  amount  to  allow  for  a shrink  fit  is  largely  a matter 
of  judgment,  in  which  the  material  and  the  construction  of 
the  article  must  be  taken  into  consideration.  Krupp  allows 
.01  inch  to  the  foot  of  diameter  in  shrinking  on  locomotive 
tires,  while  American  builders  allow  a little  more,  .012  inch 
in  1 foot  being  common  practice.  Care  should  be  taken  not 
to  allow  too  much,  since  either  the  external  piece  will  pull 
itself  apart  or  the  internal  piece  will  be  crushed  or  distorted. 

The  following  table  of  sizes  and  allowances,  adopted  by 
the  American  Railway  Master  Mechanics’  Association, 
gives  the  amount  allowed  in  several  American  shops  for 
shrinking  tires  on  car  wheels. 


§22 


ERECTING. 


37 


TABLE  II. 


SHRINK-FIT  ALLOWANCE. 


Diameter. 

Inches. 

Allowance. 

Inches. 

Diameter. 

Inches. 

Allowance. 

Inches. 

38 

.040 

56 

.060 

44 

.047 

62 

.066 

50 

.053 

66 

.070 

82.  Examples  of  Shrinking. — It  is  often  necessary 
to  shrink  a crankpin  in,  which  may  be  done  in  the  following 
manner.  The  pin  is  turned  to  the  required  size  and  the 
crank  is  then  heated  hot  enough  to  allow  the  pin  to  enter 
freely.  Care  must  be  taken  at  this  stage  of  the  proceed- 
ings to  guard  against  the  pin  sticking  in  the  hole  before 
it  is  clear  in.  A heavy  sledge  should  be  provided  on  both 
sides,  as  the  pin  may  require  a little  driving  to  carry  it 
clear  home.  If  the  crank  should  cool  too  rapidly,  the  pin 
must  be  backed  out  with  the  greatest  possible  promptness. 
When  once  in  place,  the  pin  should  be  kept  as  cool  as  possi- 
ble by  applying  waste  soaked  in  cold  water,  or  by  keeping  a 
stream  of  cold  water  flowing  on  the  pin.  Care  must  be 
taken  not  to  let  the  pin  get  as  hot  as  the  crank,  or  the  pin 
may  expand  the  hole  and  the  fit  will  then  not  be  as  tight 
as  was  intended. 

83.  Shrinking  a crank  on  a shaft  is  a job  that  is  re- 
quired to  be  done  quickly.  The  shaft  should  be  blocked  up 
at  a convenient  distance  from  the  floor,  with  the  key  seat 
up.  The  crank  should  be  heated  until  the  bore  shows  suffi- 
cient expansion  to  go  on  the  shaft  easily.  If  the  crank  is 
heavy,  it  should  be  picked  up  by  a crane  in  such  a position 
that  the  key  seat  will  be  on  top,  to  conform  to  that  in  the 
shaft.  All  dust  or  dirt  should  be  carefully  brushed  from 
the  crank,  which  should  be  quickly  shoved  up  to  the  shoulder 
on  the  shaft,  and  a temporary  key,  fitting  sidewise,  should 


ERECTING, 


38 


§ 22 


then  be  lightly  driven  in  to  keep  the  key  seat  in  line. 
Means  should  be  provided  for  holding  the  crank  against 
the  shoulder,  or  it  may  slip  back  and  grip  the  shaft  so 
tightly  that  it  can  never  be  brought  up  into  its  correct 
position.  The  permanent  key  may  be  fitted  after  the  crank 
is  cooled  off. 

84.  A Special  Heater. — A very  convenient  burner 
for  heating  parts  in  making  shrink  fits  is  shown  in  Fig.  22. 

A locomotive  piston  a is 
clamped  between  two 
wooden  pieces,  as  shown 
in  the  illustration,  and  a 
gas  burner  b,  which  em- 
bodies the  principle  of  the 
Bunsen  burner,  is  sup- 
ported centrally  in  the 
piston-rod  hole.  The 
burner  has  a number  of 
holes  on  its  circumference 
producing  as  many  jets  of 
flame,  which  strike  the 
surface  to  be  heated.  An 
ordinary  rubber  gas  tube  c 
connects  the  burner  writh 
a gas  pipe  on  the  wall. 


HOISTS  AND  CRANES. 


HOISTS. 

85.  General  Consideration.  — It  frequently  occurs 
that  the  heavy  parts  of  machinery,  and  often  the  whole 
machine  itself,  must  be  moved.  This  work,  if  it  is  done 
without  proper  appliances,  requires  the  help  of  many  persons, 
and  in  that  case  becomes  very  expensive  with  an  increase  of 
the  size  and  weight  of  the  parts  to  be  moved.  Light  machine 


ERECTING. 


n 


t 


39 


parts  may  require  no  special  appliances  for  hoisting,  or  at 
the  most  only  an  ordinary  chain  block. 

86.  Block  and  Tackle. — For  some  classes  of  work, 
and  especially  for  erecting  in  the  field,  an  ordinary  block 
and  tackle  like  the  one  shown  in  Fig.  23 
is  very  useful.  One  advantage  the  block 
and  tackle  possesses  is  that  it  is  generally 
possible  to  lift  a weight  to  a greater  height 
than  with  the  chain  block,  since  a longer 
rope  can  easily  be  reeved  in  and  is  more 
readily  obtained  than  a chain. 

Small  blocks  and  tackles  with  or  f-inch 
rope  are  often  called  handy  tackles.  The 
handy  tackle  is  especially  useful  for  draw- 
ing a weight  suspended  from  a larger  tackle 
to  one  side,  or  for  moving  machinery  sup- 
ported on  rollers. 

87.  Care  should  be  taken  to  see  that  the 
tackle  is  always  placed  in  its  most  advan- 
tageous position  for  hoisting  or  pulling.  For 
hoisting  with  the  tackle  shown  in  Fig.  23, 
the  hook  a should  be  attached  to  some 
fixed  support  above  and  the  hook  b should  be 
made  fast  to  the  work.  In  this  case  a given 
amount  of  pull  on  the  rope  c will  cause  an 
equal  pull  on  the  other  ropes  d , e,  and  fy  so 
that,  neglecting  friction,  a given  pull  on  c 
can  lift  three  times  the  load  on  the  hook  b. 

For  dragging  weights  horizontally,  the 
hook  b should  be  attached  to  the  station-  fig  23. 

ary  object  and  the  hook  a should  be  made  fast  to  the 
moving  load,  the  rope  c being  then  pulled  in  the  general 
direction  of  the  tackle.  This  has  the  advantage  of  giv- 
ing four  ropes  pulling  on  the  block  g and  hence  on  the 
hook  a. 


88.  Chain  Blocks. — A great  variety  of  chain  blocks  are 
used  in  the  machine  shop,  of  which  the  most  common  type, 


40 


ERECTING. 


§22 


known  as  the  differential  chain  block,  is  illustrated  in 
Fig.  24.  A chain  a passes  over  a differential  pulley  b , and 
about  a single-chain  pulley  c at  the  bottom.  A 
hook  is  attached  to  each  pulley,  the  upper  one  d 
being  used  to  support  the  block  from  the  ceil- 
ing, or  overhead  part,  and  the  lower  one  e for 
the  purpose  of  taking  hold  of  the  part  to  be 
raised.  The  differential  pulley  b is  provided 
with  two  chain  grooves,  the  diameter  of  one 
being  greater  than  the  diameter  of  the  other. 
As  the  chain  is  drawn  over  the  pulley  so  that 
the  latter  revolves,  a greater  length  of  chain 
per  revolution  will  travel  over  the  groove 
with  the  larger  diameter  than  over  the  one 
with  the  small  diameter.  This  being  true,  it 
will  be  seen  that  when  the  side  of  the  loose 
loop  a , which  is  on  the  large  diameter,  is 
drawn  down,  it  will  shorten  the  distance  be- 
tween the  two  pulleys  and  lengthen  the  loose 
loop.  By  drawing  down  on  the  other  side  of 
fig.  24.  the  chain  that  runs  over  the  small  diameter, 
the  distance  between  the  pulleys  is  in- 
creased. A weight  hanging  upon  the 
hook  e will  be  raised  or  lowered  accord- 
ing to  which  side  of  the  loop  is  pulled. 

Other  forms  of  chain  blocks,  in  which 
the  reduction  is  obtained  with  worms 
and  worm-gears,  or  by  means  of  spur 
gears,  are  also  used  quite  extensively. 


89.  Pneumatic  Hoists. — Shops 
provided  with  a compressed-air  plant 
use  the  air  for  many  purposes.  It  is 
particularly  useful  in  serving  work  to 
the  machine  tools,  vise,  bench,  laying- 
out  table,  etc.  The  principal  features 
of  this  hoist,  which  are  shown  in  Fig.  25, 
are  a cylinders,  in  which  slides  a piston 


Fig.  25. 


ERECTING. 


41 


§ 22 

having  a rod  that  is  supplied  with  an  eye  e at  its  lower  end. 
The  air  pipe  is  connected  to  the  air-pipe  line  by  a hose,  and 
air  is  admitted  to  the  cylinder  by  the  three-way  cock  v. , 
which  is  operated  by  the  chain  in  order  to  raise  the  weight 
that  is  attached  to  the  eye.  The  hoist  will  lift  the  length 
of  its  piston  travel  and  will  travel  on  its  runway  as  far  as 
the  hose  will  permit. 


CRANES. 

90.  Jib  Crane. — Li  mited  areas,  and  often  one  or  two 
machine  tools,  are  served  by  jib  cranes,  one  form  of  which 


is  shown  in  Fig.  26.  Heavy  cranes  of  this  type,  capable  of 
lifting  30  tons,  are  in  use  in  some  shops,  although  for  such 
heavy  work  the  traveling  crane  is  generally  preferable. 


erecting. 


,,  Trolley  System. — The  traveling  hoist 
extremely  useful  and  convenient  method  o 


furnishes 

handling 


§22 


ERECTING. 


43 


cannot  be  used.  The  run- 
way or  track  used  in  this 
system  of  shop  transpor- 
tation consists  of  I beams 
suspended  from  overhead, 
as  shown  in  Fig.  27. 

The  illustration  shows 
how  the  traveler  d may  be 
switched  from  the  main 
track  r to  a side  track  r' . 
A section  r"  of  the  main 
track  is  hinged  at  a,  and 
its  free  end  can  be  swung 
in  line  with  the  main  track 
or  side  track  by  pulling 
one  of  the  chains  c,  c.  The 
hoist  e is  attached  to  the 
traveler. 

92.  Hand  Travel- 
ing Crane. — The  travel- 
ing crane  furnishes  the 
most  modern  and  conve- 
nient means  of  shop  trans- 
portation. Cranes  of  this 
kind  are  operated  by  hand, 
by  power-driven  shafting, 
or  by  electric  motors. 

The  traveling  crane  is 
a bridge-like  structure, 
spanning  the  floor  and 
supported  on  steel  rails 
placed  on  suitable  sup- 
ports, as  is  shown  in 
Fig.  28.  This  crane  has 
a capacity  of  from  2 to  6 
tons  and  is  operated  by 
hand.  It  is  built  for  spans 


44 


ERECTING. 


§ 22 


of  30  feet  and  under.  I beams  a carry  the  rails  b on  which 
the  crane  runs.  In  the  case  of  heavy  cranes,  these  I beams 
are  replaced  by  built-up  girders.  These  runways  are  placed 
as  high  up  in  the  building  as  possible  in  order  to  get  as 
much  room  under  the  crane  as  can  be  had.  The  runway 
extends  the  whole  length  of  the  floor  or  building  and  a 
trolley  c running  on  rails  can  travel  from  one  end  of  the ' 
bridge  to  the  other,  and  hence  can  be  brought  over  any 
desired  point  on  the  floor.  Hand  cranes  like  the  one  illus-  * 
trated  are  operated  from  the  floor  in  the  following  manner. 

A shaft  d has  a pinion  e on  each  end  that  meshes  with  the 
gears  f,f;  they  are  keyed  to  the  same  shafts  to  which  the 
wheels^*,  g are  fastened.  The  shaft  d is  rotated  by  pulling 
the  chain  A,  and  the  crane  is  thus  traversed  lengthwise 
of  the  building.  A similar  mechanism  runs  the  trolley  from 
one  end  of  the  bridge  to  the  other.  The  hoisting  is  done 
from  the  floor  and  provision  is  made  for  several  men  to 
work  the  hoist  for  heavy  loads. 

93.  Power  Traveling  Crane.  — The  power-driven 
and  electrically  driven  traveling  cranes  have  the  same  gen- 
eral movements  as  are  found  in  the  hand  crane  just  de- 
scribed, but  as  they  are  intended  for  heavy  work  they  are 
built  heavier  than  the  hand  cranes.  The  power-driven  crane 
is  usually  operated  by  means  of  a square  shaft  placed  just 
below  the  bridge  and  close  to  the  runway  girder.  This  shaft 
is  carried  in  boxes  at  each  end,  and,  passing  through  a sleeve 
that  is  attached  to  the  crane,  it  transmits  its  motion  to  the 
various  trains  of  gearing  that  operate  the  different  traverses 
and  hoists.  The  great  length  and  weight  of  the  square  shaft 
makes  it  necessary  to  furnish  more  support  than  is  afforded 
by  the  boxes  and  the  sleeve.  The  additional  support  is 
given  in  the  following  manner.  The  shaft  is  made  in  sec- 
tions, with  cylindrical  bearings  turned  at  regular  intervals 
for  the  supports,  which  are  placed  under  it.  These  sup- 
ports automatically  drop  down  out  of  the  way  as  the  crane 
comes  to  them  and  return  to  their  places  when  the  machine 
has  passed  along.  The  square  shafts  are  made  in  as  long 


22 


ERECTING. 


45 


sections  as  can  be  shipped,  and  are  welded  together  in 

the  shop  where  they  are  to  run 
and  then  hoisted  into  position. 

94.  Electric  Traveling 
Crane. — The  electrically  driven 
crane  may  be  driven  by  a single 
motor  and  the  separate  parts 
may  be  run  by  trains  of  gearing, 
but  more  generally  it  has  a sep- 
arate motor  for  each  movement. 
Many  such  cranes  that  are  in- 
tended for  heavy  work  have  an 
auxiliary  hoist  in  order  to  allow 
light  work  to  be  handled  much 
quicker  than  can  be  done  with 
the  main  hoist. 

The  current  for  operating  these 
cranes  is  taken  from  wires  run 
along  the  sides  of  the  building 
just  above  the  bridge.  The  op- 
erator is  carried  in  a cage  i, 
Fig.  29,  suspended  below  and  to 
one  side  of  the  bridge,  where 
he  controls  the  various  move- 
ments by  means  of  levers, 
switches,  or  other  devices  shown 

at  j. 

95.  The  crane  illustrated  in 
Fig.  29  is  electrically  driven,  and 
has  a capacity  of  10  tons,  with  a 
span  of  54  feet;  the  same  gen- 
eral manner  of  construction  is 
followed  by  its  builders,  in  the 
construction  of  similar  cranes 
that  will  lift  as  much  as  150 
tons. 


ERECTING. 

(PART  2.) 


MACHINE  ERECTION. 


LATHES. 

1.  Systems  of  Lathe  Erection. — The  method  of 
erecting  lathes  varies  greatly  in  different  shops  and  also 
with  different  sizes  and  designs.  Some  makers  first  plane 
the  grooves  in  the  headstocks  and  tail-stocks  to  a gauge  and 
then  bore  the  boxes  of  the  headstocks  and  the  holes  for  the 
tail-stock  spindles,  while  others  reverse  the  operation,  first 
boring  the  boxes  and  the  holes  in  the  tail-stock  spindles  and 
then  planing  the  grooves  in  the  bottoms  of  the  headstocks 
and  tail-stocks.  Both  systems,  or  modifications  of  both, 
are  frequently  used  in  the  same  shop.  The  second  system 
is  generally  used  on  small  lathes,  up  to  18  inches  swing, 
while  in  the  case  of  larger  lathes  the  first-mentioned  system 
is  more  common. 

2.  Seasoning  the  Beds. — Where  extremely  accurate 
lathes,  such  as  toolmakers’  lathes,  are  to  be  made,  the  beds 
should  be  cast  several  weeks  before  they  are  to  be  used,  and 
allowed  to  season.  This  consists  in  simply  piling  them  in 
some  convenient  place  in  such  a way  that  they  will  not  be 
subjected  to  any  outside  forces,  and  allowing  the  stresses  in 

§ 23 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


C.  S.  III.— 20 


2 


ERECTING. 


§ 23 

the  casting  itself  to  become  equalized.  Where  extremely 
accurate  work  is  required,  a roughing  cut  is  taken  off  the 
surfaces  to  be  planed  and  the  beds  are  again  allowed  to  season 
for  a short  time  before  being  finished. 

3.  Machining  the  Beds. — Lathe  beds  may  be  finished 

either  on  the  planer  or  milling  machine.  For  more  accurate 
beds,  especially  for  larger  sizes,  planing  is  preferable.  The 
V grooves,  guides,  or  shears  are  usually  planed  to  gauges. 
The  outside  edges  of  the  bed  and  the  flat  top  between  the 
ways  are  also  planed.  After  the  work  leaves  the  planer, 
the  space  between  the  grooves,  the  outside  edge,  and  the 
flat  top  of  the  bed  should  be  filed  and  polished  as  soon 
as  possible,  on  account  of  the  fact  that  they  can  be  finished 
much  easier  and  in  less  time  immediately  after  planing 
than  would  be  possible  if  the  work  were  exposed  to  the 
air  of  the  shop  for  some  time.  The  reason  for  this  is 
that  the  file  takes  hold  of  the  freshly  planed  work  better 
than  it  does  after  the  surfaces  have  become  slightly 

rusted.  Some  persons  claim  that  the  reason  a file  does 

not  take  hold  of  the  surface  of  a casting  that  has  stood 

for  some  time  after  planing  is  that  the  surface  becomes 

covered  with  a thin  coating  of  grease  that  is  deposited  from 
the  air  of  the  shop. 

4.  Testing. — The  ways  are  usually  tested  by  a straight- 
edge and  then  scraped,  or,  if  necessary,  they  are  filed  and 
scraped.  However,  one  of  the  best  shops,  in  which  small 


b b 


a a 


Fig.  1. 

lathes  are  made  in  lots  of  from  25  to  100  at  a time,  uses  a 
special  surface  plate  made  as  shown  in  Fig.  1 for  each  size 
of  lathe.  This  surface  plate  has  been  fitted  up  with  great 


§23 


ERECTING. 


3 


care,  so  that  both  the  top  and  bottom  ways  a and  b match 
each  other;  it  has  a trunnion  at  each  end  and  can  be  lifted 
by  a bale  attached  to  a chain  block  or  air  lift.  The  trunnions 
permit  the  plate  to  be  turned  with  ease,  either  side  up.  The 
ways  on  the  lathe  bed  are  scraped  to  fit  the  grooves  a , a , and 
the  headstock,  tail-stock,  and  saddle  are  scraped  to  fit  the 
ways  b,  b.  The  saddle  is  sometimes  scraped  to  the  ways  on 
the  bed. 

5.  Machining  and  Fitting  Headstocks  and  Tail- 
Stocks. — The  headstocks  and  tail-stocks  of  small  lathes  are 
frequently  made  ready  for  the  boxes  and  caps  by  milling, 
while  the  larger  sizes  are  planed,  machining  them  if  possible 
by  the  gang  system ; that  is,  a large  number  are  put  on  the 
planer  table  in  line,  and  all  are  machined  together.  Jigs 
are  usually  provided  for  holding  the  pieces  on  the  milling 
machine,  and  may  also  be  employed  on  the  smaller  sizes 
when  the  work  is  done  on  the  planer.  The  legs  are  fitted 
and  bolted  to  the  bed  at  any  convenient  time,  but  it  is  gen- 
erally done  before  the  ways  on  the  bed  are  scraped. 

The  machined  castings  for  the  headstocks  and  tail-stocks 
are  next  sent  to  the  fitter;  the  boxes  and  caps  are  then  fitted 
to  the  headstocks,  and  the  tops  and  bases  of  the  tail-stocks 
are  fitted  to  each  other. 

6.  Boring  for  Headstock  and  Tail-Stock  Spindles. 

There  are  two  general  systems  for  boring  the  holes  for  the 
spindles  in  lathe  headstocks  and  the  tail-stocks.  In  the  case 
of  small  lathes,  the  boring  is  usually  done  first,  after  which 
an  arbor  is  placed  in  the  bored  holes  of  both  headstock  and 
tail-stock.  This  arbor  is  made  to  fit  the  holes  in  both  accu- 
rately, and  hence  serves  to  bring  them  into  line.  While  the 
pieces  are  held  in  line  by  means  of  the  arbor,  the  V grooves 
are  planed  in  them.  In  the  case  of  larger  lathes,  the  V’s  are 
usually  planed  first  and  the  headstock  and  tail-stock  fitted 
to  the  ways  on  the  bed.  After  this  a special  fixture  carry- 
ing a boring  bar  is  used  for  boring  the  holes  in  the  head- 
stock  and  tail-stock.  This  fixture  is  constructed  so  that  it 


4 


ERECTING. 


§23 


holds  the  boring  bar  parallel  to  the  V’s  or  ways  of  the  lathe. 
A special  jig  may  be  used  for  holding  the  headstock  and 
tail-stock  while  boring,  in  place  of  putting  them  upon  the 
bed.  After  the  boring  is  completed  and  the  V’s  are  planed, 
the  work  of  erecting  actually  begins. 

7.  Erection  and  Inspection  of  Eatlies. — Lathe 

erection  differs  somewhat  in  different  shops,  but  the  follow- 
ing may  be  taken  as  a good  illustration  of  the  general 
method  of  procedure.  The  bed,  with  the  legs  attached,  is 
placed  in  position  on  the  erecting  floor  and  leveled  until  it 
is  out  of  wind.  The  V’s  or  ways  are  tested  by  means  of 
straightedges  and  suitable  gauges.  The  headstock  and  tail- 
stock  are  then  scraped  to  fit  the  V’s. 

When  the  headstock  and  tail-stock  have  been  brought  to 
fit  the  V’s  fairly  well,  their  spindles  are  brought  into  aline- 
ment.  This  is  commonly  done  by  means  of  proof  bars,  as 


.(b) 

Fig.  2. 


shown  at  a , Figs.  2,  3,  4,  and  5.  These  proof  bars  fit  the 
boxes  of  the  headstock  and  the  bore  of  the  tail-stock  spindle. 
The  ends  b of  the  proof  bars  are  finished  by  grinding  to 


ERECTING. 


23 


exactly  the  same  diameter,  so  as  to  allow  them  to  be  used 


temporary 

/ 


ifi 

e 

- — 

in  making  measurements  for  alinement. 
saddle  c is  used  for  this  purpose. 

It  is  provided  with  a groove  fit- 
ting one  of  the  V’s  of  the  bed, 
and  carries  a slide  d to  which 
an  upright  arm  e is  fastened. 

The  headstock  and  tail-stock 
with  the  proof  bars  in  them  are 
placed  on  the  bed  some  distance 
from  the  ends.  The  temporary 
saddle  is  placed  near  one  end  of 
one  of  the  proof  bars,  and  the 
slide  d is  adjusted  until  the 
feeling  piece,  as,  for  instance, 
the  steel  rule  f,  shown  in  Fig.  3, 
will  just  fit  between  The  face  of 
the  upright  e and  the  end  b of 
the  proof  bar.  The  saddle  c is  then  shifted  to  each  end 
of  each  proof  bar,  and  the  distance  between  e and  the  end^  b 
of  the  proof  bars  tested  in  each  position.  This  is  done  with\ 
out  disturbing  the  position  of  the  upright.  The  manner  in 
which  the  feeling  piece  goes  in  shows  whether  the  head- 
stock  and  tail-stock  are  in  perfect  alinement  in  a horizontal 
plane.  If  this  is  not  the  case,  the  grooves  that  fit  on  the  V’s 
of  the  lathe  are  scraped  until  the  piece  that  is  out  of  aline- 
ment is  brought  into  perfect  alinement.  Sometimes  a 
machinist’s  indicator  or  some  form  of  micrometer  head  is 
carried  on  an  upright  e.  Such  a device  as  this  serves  to 
measure  the  amount  that  the  spindles  are  out  of  alinement. 


Fig.  3. 


8.  To  test  the  vertical  alinement  of  the  spindles,  a jack^*, 
Fig.  4,  may  be  used.  This  is  placed  on  top  of  the  parallel  c 
and  is  tested  by  adjusting  the  screw  until  it  will  just  touch 
one  end  of  the  proof  bar.  The  parallel  and  the  jack  are 
then  shifted  to  each  end  of  each  proof  bar.  The  manner  in 
which  the  jack  goes  under  the  bar  determines  which  way,  if 
any,  either  end  of  the  spindle  is  out  of  line. 


6 ERECTING.  §33 

The  method  of  testing  the  alinement  which  has  just  been 


a 


(b) 

Fig.  4. 


described  not  only  tests  the  alinement  of  the  headstock  and 
tail-stock  spindles  in  respect  to  each  other,  but  at  the  same 


time  tests  their  alinement  with  the  ways  or  line  of  motion. 


§23  ERECTING.  ? 

After  the  headstock  and  tail-stock  are  lined,  the  saddle  is 
placed  on  the  V’s  and  a round  test  piece  a,  Fig.  5,  is  placed 
against  the  slide  b.  This  test  piece  should  be  ground  exactly 
cylindrical  and  should  be  long  enough  to  project  several 
inches  beyond  the  sides  of  the  saddle.  An  arm  c is  now 
fastened  to  the  proof  bar  and  the  setscrew  d brought  in  con- 
tact with  the  bar  a.  The  proof  bar  is  then  rotated  to  the 
opposite  side,  to  the  position  shown  by  the  dotted  lines.  If 
the  screw  d does  not  show  the  saddle  to  be  square,  it  must 
be  shifted  by  scraping  the  V’s  in  the  saddle  until  the  slide  b 
is  at  right  angles  to  the  V’s,  as  shown  by  the  test  bar  a and 
screw  d. 

After  the  headstock,  tail-stock,  and^addle  are  brought 
into  alinement  with  the  V’s,  the  tail-stock  spindle  and  anchor 
are  added  to  the  tail-stock,  and  the  spindle,  back  gears,  feed- 
mechanism,  and  feed-reversing  mechanism  are  placed  in  posi- 
tion on  the  headstock.  It  is  necessary  to  have  the  set-over 
screws  in  the  tail-stock  while  lining  the  tail-stock  spindle  if 
the  two  spindles  are  to  be  brought  into  line  with  each  other. 

9.  The  apron  is  next  clamped  to  the  saddle  and  tested 
for  alinement  by  using  a proof  bar  placed  in  the  beatings 
for  either  the  lead  screw  or  feed-rod.  Measurements  for 
alinement  are  taken  from  the  bar  to  the  edge  of  the  bed  and 
to  the  top  of  the  bed.  If  necessary,  the  apron  is  brought 
into  alinement  by  filing  its  top  and  back.  The  apron  is  then 
secured  in  position  by  screws,  and  the  boxes  for  carrying  the 
lead  screw  and  feed-rod  are  placed  on  special  bearings  pro- 
vided on  the  ends  of  the  apron  proof  bar.  The  boxes  are 
then  moved  'into  contact  with  the  pads  on  the  bed,  which 
have  been  provided  to  carry  them.  These  pads  have  been 
previously  planed,  and  the  boxes  are  marked  and  then  planed 
to  fit  on  the  pads.  After  the  boxes  have  been  planed  they 
are  fastened  to  the  bed,  and  the  feed-rod,  the  lead  screw, 
and  the  remainder  of  the  feed-mechanism  and  screw-cutting 
mechanism  are  put  in  place. 

10.  Taper  Holes  in  Headstock  Spindles.  — The 

taper  hole  for  the  center  of  a live  spindle  is  put  in  by  different 


8 


ERECTING. 


§23 


methods;  its  accuracy  is  in  some  instances  very  intimately 
connected  with  the  assembling  or  erection  processes.  Some 
makers  prefer  to  rough  out  the  spindle,  particularly  if  it  is 
a small  one,  and  then  to  drill,  ream,  and  hand  ream  the  hole, 
after  which  the  spindle  is  centered  by  the  hole  and  trued 
outside,  a plug  having  been  fitted  to  the  taper  hole. 

Another  method  that  has  many  advantages  is  used  exten- 
sively for  large  spindles.  The  spindle  is  centered  and  a 
steady  rest  seat  is  turned  on  both  ends,  if  it  is  to  be  a hollow 
spindle;  the  hole  is  then  put  through.  Plugs  are  driven 
into  both  ends  if  the  hole  is  larger  than  an  ordinary  lathe 
center,  and  the  spindle  is  finished  with  the  exception  of 
the  face-plate  thread  and  the  taper  hole.  The  assembler  or 
erector  puts  the  unfinished  spindle  into  its  place,  and  if  a 
large  number  of  headstocks  are  to  be  finished,  he  puts  them 
successively  on  a lathe  bed  made  for  the  purpose  and  pro- 
vided with  a taper  attachment,  and  bores  the  taper  hole 
true,  smoothing  it  with  a hand  reamer.  He  completes  the 
work  by  cutting  the  thread  to  fit  the  face  plate.  In  large 
lathes  that  are  not  built  in  large  quantities,  the  headstock 
is  mounted  on  its  own  bed  for  boring  the  taper  hole  in  the 
spindle  and  for  cutting  the  thread;  a compound  rest  is  used 
for  boring  the  hole  in  case  the  lathe  has  no  taper  attachment. 
The  process  in  which  the  spindle  is  finished  in  its  own  bear- 
ings has  the  important  advantage  that  with  reasonable  care 
and  skill  on  the  part  of  the  erector  the  taper  hole  and  the 
thread  will  be  concentric  with  the  bearings  of  the  spindle. 

1 1 . Inspection. — All  machines  are  more  or  less  defect- 
ive, as  it  is  practically  impossible  to  make  anything  abso- 
lutely perfect.  Knowing  this,  the  builder  establishes  a limit 
within  which  the  error  will  not  materially  affect  the  working 
of  the  machine,  and  furnishes  the  inspector  with  a list  of 
such  defects  and  their  limits,  with  instructions  not  to  allow  a 
machine  to  pass  until  the  errors  have  been  brought  within 
the  allowable  limits.  The  principal  features  of  an  inspection 
prior  to  shipment  are  here  given  and  are  followed  by  a 
specimen  of  an  inspector’s  report. 


ERECTING. 


§23 


d 


1 2.  The  hole  in  fhe  headstock  spindle  is  tested  for  concen- 
tricity by  means  of  a proof  bar.  This  bar  is  ground  tapering 
to  fit  the  hole  in  the  spindle  and  is  cylindrical  the  remainder 
of  its  length.  It  may  project  a foot  from  the  spindle  for  the 
smaller  lathes  and  more,  proportionately,  for  the  larger 
ones.  By  revolving  the  spindle  and  applying  the  indicator 
to  the  bar  at  the  mouth  of  the  hole  and  again  at  the  outer 
end,  the  amount  of  error  is  easily  determined. 

The  alinement  of  both  spindles  in  reference  to  each  other 
may  be  tested  by  means  of  the 
pair  of  disks  shown  in  Fig.  6, 
which  are  made  with  taper 
shanks  a , a that  fit  the  taper 
holes  in  both  spindles.  The 

disks  b,  b are  ground  to  the  same  

diameter  and  are  faced  as  square  — 
as  possible.  They  are  placed 
one  in  each  spindle ; the  tail-stock 
is  then  moved  up  to  the  head- 
stock  and  when  the  faces  c of  the 
disks  are  brought  nearly  in  con- 

53  J . FIG.  6. 

tact,  the  amount  of  error  is 

shown  by  looking  through  both  vertically  and  horizontally. 

A pair  of  centers,  having  their  ends  beyond  the  taper, 
cylindrical  and  exactly  to  the  same  size,  with  the  ends  faced 
square,  are  sometimes  used  by  the  erector  to  determine  if 
the  spindles  are  in  line.  One  is  placed  in  each  spindle,  and 
when  the  two  are  brought  up  end  to  end,  show  very  closely 
if  there  is  any  error  in  alinement. 


b b 


a □ 


I 3.  The  leadscrew  is  particularly  liable  to  error.  This 
is  tested  for  any  deviation  from  the  true  pitch  in  lengths  of 
12  inches  at  different  points  along  the  screw.  Gearing  of 
all  sorts  is  inspected  and  tested  for  alinement  and  smooth- 
ness of  operation.  The  fits  of  all  wearing  surfaces  are 
tested,  as  well  as  the  fit  of  the  various  screws  and  binding 
and  clamping  fixtures.  No  part  is  neglected,  and  no  defect- 
ive material  or  faulty  workmanship  is  allowed  to  pass. 


10 


ERECTING. 


§23 


14.  Inspector’s  Report.  — The  inspector  is  usually 
provided  with  a printed  blank  for  reporting  each  lathe.  The 
serial  number  is  stamped  on  the  lathe  and  this  appears  on 
the  report,  which  is  filed  in  the  office  for  use  should  com- 
plaint be  made  or  repairs  ordered.  Such  a report  is 
appended. 

INSPECTOR’S  REPORT. 


ILM 

Lot  No.  V?*?. 


Engine  Lathe. 

Inspection  No...!  Q '..0.3 


Spindle  runs  at  mouth,  

" “ end  of  12-inch  bar,  i0^ . 


“ lines  with  ways, 

Tail  Stock  “ " “ 

Test  piece  for  boring  8 inches,  ) 

shows  large  at  front  end  1 ^ 

Face  Plate  squares  up  concave,  ..fa* 

Taper  Attachment  Slide  Ways  t 
with  Ways  on  Bed,  J 
Back  Gears  run, , 


Ver.  u- 


^or- 


Chuck  runs, 

Rest  Binder. 

Lead  Screw,  per  foot 


It^jl 


W< 


, u.  s.  h.y3^:Jl..M0T3~ 

&L 


PRENTICE  B 


it 


COMPANY. 


PLANER  ERECTION. 

15.  Systems  of  Planer  Erection. — In  planer  erec- 
tion the  principal  points  to  be  considered  are  that  the  system 
must  be  such  as  to  quickly  and  cheaply  assemble  the  parts 
so  that  they  will  all  be  in  their  proper  relation  to  each  other 
and  that  the  alinement  of  the  various  parts  will  be  perfect 
within  the  required  limits.  Small  planers  can  be  erected 


23 


ERECTING. 


11 


much  easier  than  large  ones,  owing  to  the  fact  that  there  is 
very  ^little  or  no  appreciable  spring  in  their  beds.  When 
manufacturing  small  planers,  it  is  possible  to  make  the  parts 
so  accurately  by  means  of  gauges  and  templets  that  they 
can  be  assembled  and  made  practically  interchangeable.  In 
the  case  of  large  planers,  it  is  impossible  to  make  the  parts 
interchangeable,  on  account  of  the  fact  that  the  bed  depends 
on  the  foundation  for  its  support,  it  being  impracticable  to 
make  a casting  large  enough  to  insure  perfect  rigidity  in 
the  bed.  For  this  reason,  in  the  case  of  large-sized  planers, 
it  is  necessary  to  treat  each  machine  by  itself.  All  the 
points  in  the  erection  of  a small  planer  are  involved  in  the 
erection  of  a large  planer,  and  many  other  complicating 
factors  come  in;  hence,  the  erection  of  a planer  of  this  class 
will  be  given  in  detail. 

16.  Classes  of  Planers. — For  convenience  in  treat- 
ment, planers  may  be  divided  into  three  classes  : small, 
which  plane  up  to  24  inches  square ; medium-sized,  which 
plane  from  24  to  40  inches  square;  and  large  planers,  which 
plane  larger  than  40  inches  square.  Small-sized  planers  are 
usually  provided  with  a single  head  for  carrying  the  tool, 
the  head  being  placed  on  the  cross-rail  between  the  hous- 
ings. Most  medium-sized  planers  have  but  a single  head, 
although  some  of  the  larger  ones  are  provided  with  two  heads 
on  the  cross-rail.  The  larger  planers  are  all  provided  with  two 
heads  on  the  cross-rail  and  with  one  head  on  each  upright. 

Planers  may  also  be  divided  into  two  classes  in  regard  to 
their  construction;  that  is,  into  those  having  double  hous- 
ings, or  closed  planers,  and  those  having  but  one  housing,  or 
open-side  planers.  The  erection  of  either  type,  as  far  as  the 
general  principles  are  concerned,  does  not  differ  greatly, 
and  the  erection  of  the  closed  type  involves  the  bringing  of 
the  housings  parallel,  and  hence  planers  of  this  type  will  be 
considered.  In  the  case  of  planers  that  are  intended  to 
plane  120  inches  and  upwards,  provision  is  frequently  made 
for  handling  the  work  that  will  not  pass  between  the  hous- 
ings at  all.  This  is  accomplished  by  placing  a floor  plate  on 


12 


ERECTING. 


23 


one  or  both  sides  of  the  bed  about  half  way  between  the 
front  of  the  housings  and  the  end  of  the  bedplate.  A post 
or  posts  are  located  on  this  floor  plate  and  provided  with 
vertical  guides  carrying  one  or  more  heads.  These  uprights 
can  be  moved  toward  or  away  from  the  planer  bed,  and  the 
heads  carrying  the  tools  can  be  fed  up  or  down  the  uprights. 
This  provides  for  the  planing  of  surfaces  at  right  angles  to 
the  face  of  the  table  or  very  large  work.  With  this  device 
the  casting  rides  back  and  forth  on  the  table.  When  the 
castings  are  still  larger,  they  are  sometimes  placed  on  the 
floor  plate,  and  the  tools  are  carried  by  heads  placed  on 
the  uprights  bolted  to  the  planer  table,  the  work  standing 
still  and  the  tool  being  moved  with  the  planer  table. 

17.  Precautions  in  Regard  to  Castings.  — All 

castings  for  planers  should  be  made  from  good  close-grained 
iron.  The  castings  for  the  table  should  be  of  a soft  but 
tough  nature,  so  that  the  upper  surface  can  be  planed  true 
at  one  setting  of  the  tool,  for  if  the  casting  were  hard  it 
would  wear  the  tool  enough  to  throw  the  surface  appreciably 
out  of  true.  Very  large  planer  beds,  and  occasionally  large 
planer  tables,  are  made  in  two  or  more  pieces  and  joined  by 
means  of  bolts  and  dowel-pins. 

18.  Precautions  Necessary  in  Machining. — All 

the  larger  castings  for  the  planer  should  be  planed  to 
carefully  tested  gauges,  and  every  angular  surface  tested 
to  make  sure  that  the  angle  is  correct.  The  work  should  be 
tested  with  a straightedge  on  the  machine  to  make  sure  that 
the  planer  is  not  working  concave  or  convex.  Care  taken 
in  planing  these  parts  will  reduce  the  work  of  the  fitter  and 
erector.  Long  beds  or  tables  that  are  made  in  sections 
should  have  their  ends  planed  perfectly  square  and  should 
be  bolted  together  as  securely  as  possible  with  fitted  bolts 
and  dowels.  After  all  machine  work  is  done,  the  erection 
proper  begins. 

19.  Supporting  the  Bed. — The  bed  a,  Fig.  7,  is  sup- 
ported on  cast-iron  parallel  blocks  b placed  6 or  8 feet  apart 


ERECTING. 


13 


§23 


along  the  whole 
length  of  the  bed. 
Planed  cast-iron 
wedges  c , arranged 
as  adjustable  paral- 
lels, are  placed  be- 
tween the  parallel 
blocks  b and  the 
bed.  A clamp  jack  d 
is  placed  under  the 
bed  at  each  side 
just  forward  of  the 
housings.  This  may 
be  removed  if  nec- 
essary while  putting 
in  the  driving  gear- 
ing. The  arrange- 
ment of  all  the 
blocking  under  the 
uprights  should  be 
such  that  none  of 
it  will  interfere  with 
the  driving  and 
feed-mechanism  du- 
ring erection.  As 
these  details  vary  in 
different  machines, 
the  blocks  must  be 
arranged  to  suit 
each  different  ma- 
chine. It  is  best  to 
put  the  uprights  e 
in  their  places  on 
the  bed  before  the 
leveling  operation, 
as  the  addition  of 
their  weight  is  lia- 
ble to  throw  the  bed 


14 


ERECTING. 


§23 


out  of  level  again  if  they  are  placed  in  position  afterwards. 
In  some  cases  the  uprights  e are  supported  on  erecting  jacks 
in  place  of  blocking,  as  this  facilitates  adjustment  of  the 
parts  during  leveling. 

20.  Leveling  the  lied.  — Several  methods  may  be 
followed  in  leveling  a planer  bed,  depending  on  the  tools  at 
hand.  They  all  require  considerable  care.  The  process 
here  described  will  give  very  good  results  if  the  work  is 
carefully  done.  The  leveling  is  done  as  follows:  A pair  of 
V-shaped  parallels  f,  about  3 feet  long,  are  placed  one  in 
each  of  the  ways  or  V’s  of  the  bed.  These  parallels  have 
been  scraped  as  nearly  true  as  it  is  possible  to  make  them, 
and  they  may  have  center  lines  on  them.  A sensitive  level 
is  used  on  the  top,  and  one  side  of  the  bed  is  carefully 
leveled  by  moving  this  parallel,  short  distances  at  a time, 
over  the  entire  length.  The  other  parallel  is  used  in  a 
similar  manner  in  the  other  V,  and  by  placing  a straightedge 
across  both  of  the  parallels  and  using  the.  level  on  it,  the 
work  is  leveled  crosswise.  The  operation  of  first  leveling 
one  side  and  then  cross-leveling  to  the  other  is  repeated 
several  times,  or  at  least  until  no  further  errors  can  be 
detected. 

21.  Setting  the  Housings. — The  housings  are  now 
tested  and  brought  exactly  plumb  by  placing  a straightedge 
across  the  blocks  lying  in  the  V’s  and  using  a large  square 
on  the  straightedge.  In  the  case  of  large  planers  having  a 
very  heavy  cross-rail  and  heads,  some  makers  do  not  attempt 
to  bring  the  housings  exactly  plumb  on  their  faces,  but 
allow  them  to  lean  back  yowo  inch  f°r  every  foot  in  height, 
as  the  weight  of  the  cross-rail  and  heads  will  bring  the 
housings  forwards  somewhat,  and  experiment  has  shown 
that  this  allowance  will  about  correct  the  error  from  this 
cause.  The  housings  are  squared  both  sidewise  and  in 
front,  and  the  distances  between  them  at  the  top  and  bottom 
are  made  equal. 

In  gauging  these  distances  on  a large  planer,  use  may  be 
made  of  the  device  illustrated  in  Fig.  8 (a),  which  consists 


ERECTING. 


15 


§23 

of  a wooden  bar  made  of  white  pine  or  some  other  light  wood, 

and  fitted  with  screws  at  each  end.  The  wooden  bar  should 

be  1J  to  2 inches 

shorter  than  the  dis- 

tance  between  the 

housings,  and  the 

screws  may  be  simply 

21-inch  wood  screws 

. Fig.  8. 

with  their  heads 

filed  off  and  the  ends  pointed  and  rounded,  as  shown  in 
detail  in  Fig.  8 ( b ).  The  wooden  stick  may  be  tapered  from 
the  center  toward  both  ends,  and  in  the  case  of  a rod  for 
measuring  a distance  of  approximately  10  feet,  the  wooden 
strip  would  have  to  be  about  1J  in.  X 2-J-  in.  in  the  center. 
The  advantages  of  the  wood  are  that  it  is  lighter  than  metal 
and  that  it  is  not  affected  so  much  by  expansion  and  con- 
traction due  to  varying  degrees  of  temperature.  This  dis- 
tance between  the  housings  on  a large  planer  is  not  made  any 
fixed  distance,  the  only  object  being  to  make  it  the  same 
at  the  top  and  the  bottom,  and  hence  this  device  becomes 
only  a large  inside  caliper. 

During  the  operation  of  setting  the  housings  parallel,  the 
gauge  is  set  to  the  smallest  distance,  whether  it  be  at  the 
top  or  bottom,  and  is  then  transferred  to  the  wider  end, 
the  amount  it  is  necessary  to  move  the  housings  being 
determined  by  introducing  pieces  of  sheet  metal  or  paper 
between  the  screw  and  the  casting.  By  measuring  these 
pieces  with  the  micrometer,  it  is  possible  to  tell  just  how 
much  the  housing  must  be  moved. 

After  the  housings  are  perpendicular  and  parallel,  the 
girder  or  top  rail  is  squared  off  to  the  length  indicated  by 
this  gauge  and  bolted  in  position.  In  the  case  of  large 
planers,  no  attempt  is  made  at  interchangeability  in  this 
respect,  but  each  top  cross-rail  is  fitted  to  its  individual 
planer. 

22.  Placing  the  Table  and  Driving  Mechanism. 

The  ways  on  both  table  and  bed  are  fitted  to  a good  bearing 


16 


ERECTING. 


§23 


by  scraping  to  surface  plates.  The  driving  mechanism  is  put 
in  place.  The  table  may  then  be  put  in  place  also,  and  any 
scraping  necessary  to  true  it  to  the  ways  is  done,  after  which 
the  thickness  of  the  table  rack  is  determined;  the  rack  is 
planed  to  the  required  thickness  and  secured  to  the  table. 

23.  Squaring  the  Cross-Rail. — The  cross-rail  must 
be  set  true  to  the  V’s  in  which  the  planer  table  slides.  One 

manner  of  accomplishing  this 
is  illustrated  in  Fig.  9.  The 
table  a is  run  back  far  enough 
to  expose  the  V’s  under  the 
cross-rail  and  two  cylindrical 
pieces  b,  b'  of  exactly  the 
same  diameter  are  introduced 
into  the  V’s.  A square-nosed 
tool  c is  placed  in  the  tool 
I d post  and  brought  over  one  of 
the  cylinders  b.  The  tool  is 
then  tested  until  the  feeling 
piece  can  just  be  moved 
between  the  cylinder  and  the 
tool.  Another  method  is  to 
use  a machinist’s  indicator  in 
place  of  the  tool,  and  bring  the  point  of  the  indicator  in 
contact  with  the  cylinder.  The  tool  or  indicator  is  now  run 
to  the  opposite  side  of  the  planer  and  adjusted  over  the 
cylinder  b' . If  b'  is  found  to  be  higher  or  lower  than  b,  the 
error  must  be  corrected  by  adjusting  one  end  of  the  cross- 
rail up  or  down.  Some  makers  find  that  a sufficiently  close 
adjustment  can  be  obtained  by  moving  one  of  the  gears  k 
or  k'  one  tooth,  so  as  to  raise  or  lower  one  end  of  the  cross- 
rail this  amount.  If  this  adjustment  is  not  close  enough,  a 
small  amount  may  be  scraped  off  the  hub  of  one  of  the 
gears.  Other  makers  leave  one  of  the  pinions  m or  in'  loose 
until  the  adjustment  has  been  made,  after  which  they  key 
it  in  place.  Still  others  attach  one  of  the  pinions,  as  by 
means  of  a setscrew,  as  shown  at  n. 


m>r  n m 


!%□  -%r^* 

5 

r J? 

1 fie 

si  \/h 

L 

f 

i 

iy  I / 

r 

b b 

y^_ 

u 

i 

Fig.  9. 


§23 


ERECTING. 


17 


The  cross-rail  is  moved  up  and  down  by  two  screws  oper- 
ated by  the  gears  k and  k' . When  one  end  of  the  rail  is 
found  to  be  low,  it  should  be  raised  the  proper  amount.  In 
Fig.  9 this  can  be  accomplished  by  loosening  the  screw  n 
and  turning  the  gear  in'  the  desired  amount.  By  repeating 
these  trials  the  cross-rail  can  be  brought  into  such  a posi- 
tion that  the  tool  and  feeling  piece,  or  indicator,  will  give 
the  same  reading  over  both  cylinders  b and  b' . The  vertical 
screws  carrying  the  cross-rail  should  always  be  adjusted  in 
such  a manner  as  to  raise  the  cross-rail,  on  account  of  the 
fact  that  this  will  take  up  any  lost  motion  or  backlash 
between  the  nuts,  the  feed-screws,  and  the  uprights.  For 
this  reason  it  is  always  better  to  raise  the  low  end  of  the 
cross-rail  rather  than  to  lower  the  high  end.  The  feed- 
mechanism  and  the  mechanism  for  raising  the  cross-rail  by 
power,  together  with  the  oiling  device,  are  all  put  in  place 
and  tested,  after  which  the  machine  is  tested  to  see  that  it 
is  within  the  allowable  limits  of  error. 

After  the  cross-rail  has  been  adjusted  parallel  to  the  V‘s, 
a light  cut  should  be  taken  over  the  top  of  the  table.  The 
head  g should  then  be  set  vertically  by  means  of  a square. 
In  the  case  of  very  large  planers  the  table  is  not  trued  in 
place  by  the  manufacturer. 

24.  Preparation  of  Planer  for  Shipment. — Small 

and  medium-sized  planers  are  generally  shipped  with  the 
principal  parts  in  place  and  all  bright  parts  coated  with  a 
slush  of  oil,  or  some  other  protective  coating,  to  prevent 
rusting.  The  lighter  and  small  parts  are  crated  to  prevent 
breakage  and  the  whole  mounted  on  skids  for  convenience 
in  handling.  Larger  planers  are  taken  apart,  the  smaller 
pieces  being  boxed  and  the  fitted  faces  of  the  larger  ones 
crated.  All  finished  surfaces,  in  all  cases,  are  slushed  or 
given  a protective  coating  before  shipping.  The  smaller 
planers  have  their  tables  carefully  trued  in  place  before 
leaving  the  manufacturers,  but  the  larger  ones  are  usually 
shipped  with  the  table  just  as  it  comes  from  the  planer  on 
which  it  was  finished. 


C.  S.  III.— 21 


18 


ERECTING. 


§23 


ERECTION  OF  PLANERS  IN  PLACE. 

25.  Large  Planers. — In  the  case  of  all  large  planers, 
the  beds  of  which  rest  on  the  foundation,  the  bed  is  placed 
on  the  foundation  and  leveled  by  means  of  wedges  or  jacks. 
The  housings  are  bolted  in  place  and  the  bed  leveled  by  the 
process  described  in  Art.  20.  The  housings  are  also  set 
perpendicular  to  the  bed.  The  cross-rail  and  its  elevating 
mechanism  are  then  placed  in  position. 

The  cross-rail  may  then  be  tested  to  see  that  it  is  parallel 
with  the  V’s,  as  described  in  Art.  23.  The  feed-mechanism 
may  be  put  in  by  other  men  while  these  operations  have 
been  going  on,  and  after  the  cross-rail  is  adjusted  parallel 
to  the  V’s,  the  table  should  be  tested.  If  it  is  found  that 
the  table  is  not  parallel  with  the  cross-rail,  a light  cut  should 
be  taken  over  it.  After  this  is  accomplished,  the  head  g, 
Fig.  9,  must  be  set  to  plane  perpendicular.  In  the  case  of 
a large  planer  there  will  probably  be  two  heads  on  the  cross- 
rail. They  are  both  set  as  near  perpendicular  as  possible 
by  means  of  a square.  After  this,  the  sides  f,  f of  the 
table  may  be  trued  down  by  means  of  tools  set  in  the  heads, 
and  the  angle  at  the  edge  of  the  table  tested  by  a square. 
If  this  is  found  to  be  true,  the  mark  h is  placed  on  the 
saddle  opposite  the  zero  mark  of  the  graduations  on  the 
head,  as  practically  all  planers  are  shipped  from  the  factory 
with  their  heads  graduated,  but  without  the  zero  mark  on 
the  saddle  being  located. 

If  the  planer  is  provided  with  side  heads  on  the  uprights  i 
and  i\  they  may  be  tested  by  bolting  a casting  as  indicated 
by  the  dotted  lines  at  j to  the  face  e of  the  table  and  then 
taking  cuts  from  the  sides  of  this  casting  by  means  of  the 
side  heads,  the  upper  face  of  the  casting  having  been  trued 
by  means  of  a tool  in  one  of  the  heads  on  the  cross-rail. 

2(5.  Securing  tlie  Planer  to  the  Foundation. 

After  the  planer  is  erected  and  all  the  tests  have  been  made 
and  everything  adjusted  correctly,  it  should  be  secured 
to  the  foundation.  This  may  be  accomplished  by  ramming 
any  suitable  cement  between  the  bottom  of  the  bed  and  the 


ERECTING. 


19 


§23 

top  of  the  foundation.  Sometimes  iron  chips  and  sal  ammo- 
niac are  used.  In  other  cases  a regular  Portland  cement 
mortar  is  employed,  while  in  some  cases  melted  sulphur  is 
poured  under  the  bed.  After  the  cement  is  in  place  the 
planer  should  not  be  used  until  time  has  been  given  for 
the  cement  to  harden.  In  cases  where  the  foundation  is  on 
yielding  ground,  and  it  is  not  practicable  to  obtain  a perma- 
nent foundation,  planers  are  sometimes  left  set  on  wedges  or 
jacks  and  are  leveled  up  frequently  to  keep  them  in  line. 

The  bed  of  the  planer  should  be  tested  lengthwise  with  a 
straightedge  to  see  whether  or  not  it  is  planing  concave  or 
crowning.  This  precaution  is  especially  necessary  in  the 
case  of  very  long  planers.  It  is  convenient  to  have  the 
planer  table  set  level  so  that  a spirit  level  may  be  used  on 
any  part  of  it.  In  this  case,  by  applying  the  spirit  level  to 
different  parts  of  the  table  it  will  indicate  whether  the  planer 
is  planing  convex  or  concave. 

27.  Planers  Having  Legs. — Small  and  medium-sized 
planers  are  shipped  from  the  factory  with  all  their  parts  in 
place,  and  hence  do  not  need  as  careful  attention  in  erec- 
tion as  do  the  larger  sizes,  which  have  to  be  assembled  on 
their  foundations.  It  is  usually  sufficient  to  drive  wedges 
under  the  legs  until  the  table  is  level.  The  cross-rail  is  then 
tested  to  see  that  it  is  parallel  to  the  top  of  the  table,  and  if 
found  so,  no  further  adjustment  need  be  made.  If  it  is  not 
parallel,  the  table  should  be  run  back,  and  the  cross-rail  set 
parallel  to  the  V’s,  as  described  in  Art.  23.  After  this,  a 
light  cut  should  be  taken  over  the  table  and  the  heads  set 
to  plane  vertically. 

In  the  case  of  very  small  planers,  the  beds  are  usually 
stiff  enough  so  that  very  little,  if  any,  adjusting  is  necessary 
when  setting  them  up,  all  the  adjustment  being  made  by 
the  manufacturer;  but  even  in  this  case  it  is  well  to  go 
through  the  entire  series  of  tests,  if  accurate  work  is  to  be 
required  from  the  machine. 

28.  Setting  Planer  Heads. — The  amount  of  accuracy 
required  in  setting  the  heads,  either  on  a large  or  small 


20 


ERECTING. 


§23 

planer,  depends  very  largely  on  the  character  of  the  work 
to  be  done  on  the  machine.  If  the  work  will  all  be  simply 
roughing  and  surfacing,  the  zero  mark  h,  Fig.  9,  may  be 
placed  accurately  enough  by  adjusting  the  head  to  any 
available  square  and  scribing  or  cutting  the  mark  on  the 
saddle;  while  if  a large  amount  of  angular  work  is  to  be 
done  on  the  planer,  it  will  be  necessary  to  face  down  one  or 
more  castings  to  see  that  the  mark  is  accurately  located. 
Sometimes  it  is  well  to  put  on  a provisional  or  temporary 
mark  and  then  test  each  piece  of  work  as  it  comes  from  the 
planer  until  sufficient  information  has  been  obtained  to  locate 
the  mark  accurately. 


MILLING-MACHINE  ERECTION. 

29.  Introduction. — There  is  a large  class  of  machines 
in  which  the  erection  cannot  all  be  done  at  one  time,  but 
must  be  carried  on  between  the  various  operations  in  the 
machine  work.  This  is  on  account  of  the  fact  that  some  parts 
of  the  machine  must  be  completed  before  other  parts  can  be 
machined  or  fitted.  This  is  especially  true  of  very  large 
machines  and  of  some  comparatively  simple  machines  in 
which  a number  of  parts  are  interdependent.  The  milling 
machine  as  erected  in  at  least  one  large  shop  forms  a good 
example  of  this  class  of  erection. 

30.  Planing  the  Column. — The  column  a,  Fig.  10,  is 
first  fastened  on  a planer  table  with  the  face  b up.  Great 
care  must  be  taken  to  see  that  the  casting  is  not  sprung 
by  clamping.  The  face  b and  the  inclined  surfaces  c,  c'  are 
carefully  planed  to  a standard  gauge.  The  general  form  of 
these  parts  is  shown  in  Fig.  11. 

31.  First  Drilling  Operation. — After  the  planing  is 
complete,  the  frame  is  taken  to  a drill  press  and  all  the 
holes  that  do  not  require  exact  location  drilled.  This  includes 
those  for  fastening  the  column  to  the  floor,  for  the  tool 
shelf,  the  tool-cupboard  door,  etc.  A special  jig  that 
clamps  on  to  the  face  b by  means  of  the  surfaces  c and  c'  is 
used  to  guide  drills  and  reamers  for  forming  the  holes  for 


§23 


ERECTING. 


21 


the  elevating  screw  d ',  the  knee , stop-rod  e , and  the  vertical 
feed-shaft  f.  This  jig  must  not  be  confused  with  the  large 
drilling  and  boring  jig  described  later,  but  is  simply  an 


angle  plate  that  is  clamped  to  the  face  b and  carries  bush- 
ings for  locating  the  holes  mentioned. 

32.  Fitting  the  Surface  for  Carrying  the  Knee. 

After  the  first  drilling  operation  is  completed,  the  column  is 


22 


ERECTING. 


g 23 

laid  on  its  back  and  the  surface  b,  Fig.  10,  scraped  to  a surface 
plate.  After  this,  the  angular  surfaces  c 
and  c' , Figs.  10  and  11,  are  scraped  to  a 
special  surface  plate  or  straightedge  of 
the  pattern  shown  in  Fig.  12.  The  exact 
angle  between  the  surfaces  has  to  be 
determined  by  means  of  a gauge.  The  surfaces  a and  a' 


b 


Fig.  11. 


of  the  straightedge  are  scraped  and  fitted  perfectly  true. 

33.  Painting  the  Column. — After  the  scraping  is 
complete,  the  surface  of  the  casting  is  filled,  rubbed  down, 
and  painted,  all  but  the  finishing  coat  being  applied  at  this 
time.  The  finishing  coat  is  not  given  until  after  the  machine 
has  been  inspected. 

34.  Boring  Operations  on  the  Column.  — After 
the  scraping  is  completed,  the  column  a is  placed  in  the 
jig  b , Fig.  13.  The  surface  b,  Fig.  10,  rests  on  a scraped 
surface  in  the  jig,  and  the  surfaces  c and  c\  Figs.  10  and  11, 
are  brought  in  contact  with  the  gibs  in  the  jig,  the  fixed  gib 
being  shown  at  c,  Fig.  13,  and  on  the  opposite  side  there  is 
an  adjustable  gib  that  is  held  in  position  by  means  of  set- 
screws. This  secures  the  column  in  its  proper  relation  to 
the  jig,  after  which  the  holes  for  the  spindle^',  for  the  sup- 
porting arm  //,  and  the  back  gear-shaft  z,  Fig.  10,  are  all 
bored  in  their  proper  positions.  While  these  holes  are  being 
bored,  the  boring  bar  is  supported  at  each  end  in  hardened- 
steel  bushings,  and  is  driven  by  means  of  a floating  driver 
carrying  two  universal  couplings.  This  method  of  driving 
the  boring  bar  prevents  all  danger  of  the  spindle  of  the  drill 
press  springing  it  out  of  line  with  the  bushings.  The  holes 


ERECTING. 


23 


§ 23 


are  both  bored  and  reamed  while  the  column  is  held  in  the 
jig.  This  method  of  procedure  insures  the  holes  mentioned 


being  at  right  angles  to  the  face  b,  Fig.  10,  and  hence  in  the 
proper  relation  to  the  table. 

35.  Fitting  the  Various  Parts. — After  the  holes 
for  the  spindle  gt  the  supporting  arm  /z,  and  the  back  gear- 
shaft  -S',  Fig.  10,  have  been  bored  and  reamed,  the  column  is 
removed  from  the  jig  and  placed  in  an  upright  position  on 
the  floor.  The  boxes  in  which  the  spindle  runs  are  then 
fitted  in  place  by  grinding. 

The  knee  j,  Fig.  10,  is  planed  up  and  its  upper  face 
scraped  to  surface  plates  in  a manner  similar  to  that  used 
in  scraping  the  surfaces  b , c,  and  c' , Figs.  10  and  11.  The 
face  that  is  to  fit  the  upright  of  the  column  is  also  fitted, 
and  care  must  be  taken  to  see  that  these  two  surfaces  are  at 
right  angles  to  each  other.  After  this  the  knee  is  fitted  to 
the  upright  by  scraping  the  upright  face  of  the  knee  until 
the  horizontal  face  comes  square  with  the  surface  b , Fig.  10. 

The  spindle  that  has  been  accurately  ground  with  tapered 
bearings  is  now  fitted  into  its  place  by  scraping  the  boxes 
to  bring  the  spindle  true  with  the  top  of  the  knee.  Care 
should  be  taken  to  see  that  the  spindle  is  true  in  both  the 


24  ERECTING.  § 23 

horizontal  and  vertical  planes.  The  scraping  also  serves  to 
give  the  spindle  a good  bearing  in  the  boxes. 

After  the  knee  and  spindle  have  been  fitted  up,  the  clamp 
bed  k and  the  table  q , Fig.  10,  are  fitted  in  place,  each  one 
being  adjusted  to  the  parts  already  in  place.  The  index 
head  o and  tail-stock  center  p are  fitted  up  elsewhere  and 
placed  on  the  table  after  it  has  been  accurately  fitted. 

The  overhanging  arm  h is  fitted  parallel  with  the  spindle 
by  scraping  the  holes  in  the  casting  through  which  it  passes. 
The  outboard  bearing  or  support  r is  fitted  to  the  arm  h and 
the  hole  n drilled  and  reamed  by  means  of  tools  in  the 
spindle.  This  insures  the  hole  in  the  outboard  bearing  being 
in  line  with  the  spindle.  The  diagonal  braces  s for  the  arm 
and  all  other  minor  details  are  fitted  as  opportunity  offers. 

36.  Erecting  Trucks. — For  erecting  any  machine, 
such  as  a milling  machine,  it  is  handy  to  have  erecting 
trucks  fitted  to  contain  all  the  small  parts  of  the  machine. 
When  an  order  for  a number  of  machines  is  placed  in  a shop, 
many  of  the  small  parts  are  made  and  kept  in  stock.  When 
the  larger  castings  come  on  the  floor  and  the  work  of  erec- 
tion begins,  the  man  in  charge  of  the  erection  takes  to  the 
stock  room  as  many  trucks  as  he  has  machines  to  erect,  and 
puts  the  necessary  stock  for  each  machine  on  the  trucks. 
These  trucks  are  then  placed  opposite  the  castings  for  the 
machine  with  which  they  are  to  go.  When  this  practice  is 
followed  much  time  will  be  saved,  as  the  erector  will  always 
have  the  necessary  parts  at  hand. 

37.  Inspection  of  Milling  Machines. — The  machine 
now  goes  to  the  inspector,  who  carefully  tests  all  parts  and 
motions  for  accuracy,  testing  the  knee  at  the  highest  and 
lowest  positions;  also  the  clamp  bed  at  its  inner  and  outer 
positions  and  the  table  at  both  ends  of  its  travel.  A carefully 
ground  steel  testing  bar,  one  end  of  which  is  ground  to  fit 
the  tapered  center  hole  of  the  spindle,  is  placed  in  the  spindle, 
care  being  taken  to  see  that  both  the  hole  and  the  test  bar 
are  clean  before  it  is  introduced.  The  parallel  part  of  the 
bar  projects  from  the  spindle  to  the  outer  end  of  the  knee. 


ERECTING. 


25 


§ 33 

No.  Universal  Milling  Machine. 


Lot Construction  No Serial  No. 


Spindle  runs  at  mouth, ; end, 

“ with  knee  in  Ver ; Hor 

“ “ frame  in  drop, ; width, 

“ “ overhanging  arm, in inches. 


“ “ center  in  O.  H.  arm,  high ; low.  . 

“ “ bushing  in  O.  H.  arm,  high ; low 

“ “ surface  of  platen,  length ; width. 

Slot  with  ways  of  platen, 

Spiral  Head  Spindle  runs  at  mouth, ; end, 

“ “ “ with  slot, 

“ “ “ “ center  of  slot, 


“ “ “ “ back  center  in  Hor ;Ver. ... 

“ “ “ “ platen  when  at  90°, 

“ “ “ “ main  spindle  when  at  90°, ....  . 

Eccentricity  of  swivel  bed  with  main  spindle, 

Collet  runs  at.  mouth, ; end, 

( Main  Spindle, 

Chuck  runs  out  on  -! 

( Spiral  Head  Spindle, 

Vise  out  of  parallel  with  platen  in  its  width, 

Back  gears  run, 

Passed, 190.  . .by 

Brown  & Sharpe  Mfg.  Co.  Inspector. 

* • • 

REMARKS : 


26 


ERECTING. 


§23 


The  spindle  and  the  test  bar  are  then  revolved,  and  the 
amount  that  the  test  bar  runs  out  of  true  both  at  the  spindle 
and  at  the  outer  end  is  carefully  noted  by  means  of  an  indi- 
cator reading  to  thousandths  of  an  inch.  The  test  bar  may 
also  be  used  for  measuring,  by  means  of  an  indicator,  to  see 
that  both  ends  of  the  table  are  the  same  distance  from  the 
spindle.  The  inspector  is  given  a list  of  the  allowable  vari- 
ations in  the  different  parts  of  the  machine,  and  he  must  not 
pass  a machine  until  all  errors  have  been  corrected  so  that 
the  variation  shall  not  exceed  the  allowable  limit.  In  the 
case  of  a universal  milling  machine,  the  universal  head  and 
tail-stock  .center  are  also  tested.  In  testing  the  universal 
head,  a test  bar  similar  to  the  one  used  in  testing  the  spindle 
is  employed,  in  order  to  determine  whether  or  not  the  spindle 
of  the  universal  or  spiral  head  runs  true.  The  vise  and 
chuck  are  also  tested  to  see  whether  or  not  they  are  true. 

38.  Inspector’s  Report. — All  information  obtained 
from  the  inspection  should  be  entered  on  a report  similar  to 
the  accompanying  one.  Each  machine  is  given  a serial  num- 
ber, and  these  reports  are  filed  at  the  office,  so  that  in  the  case 
of  any  trouble  arising  or  any  repairs  being  required  for  a 
given  machine,  an  exact  record  of  its  condition  when  it  left 
the  shop  is  available. 


ENGINE  ERECTION. 

39.  Equipment  Necessary. — The  manner  of  erecting 
an  engine  depends  both  on  the  equipment  at  hand  and  the 
style  of  the  engine.  Where  medium-sized  or  heavy  engines 
are  to  be  erected,  traveling  cranes  should  be  provided  for 
handling  the  heavy  parts,  as  they  can  accomplish  the  work 
much  more  quickly  and  easily  than  any  other  system  of 
handling  device.  Another  advantage  of  the  traveling- 
crane  system  is  that  the  traveling  crane  commands  the 
entire  erecting  floor.  The  crane  should  have  sufficient 
height  of  lift  to  place  in  position  the  highest  parts  of  any 
machine  built  in  the  shop.  Where  very  high  work  is  to  be 
erected,  it  is  sometimes  necessary  to  set  the  base  in  a pit  so 


§23 


ERECTING. 


27 


that  the  highest  parts  will  not  come  above  the  crane.  This 
is  especially  true  in  erecting  vertical  engines.  Some  shops 
making  a specialty  of  vertical  engines  have  two  sets  of 
traveling  cranes,  one  above  the  other,  the  lower  one  intended 
for  handling  the  heavier  pieces  and  the  upper  one  for 
handling  the  upper  portion  of  the  engine  and  the  light 
pieces.  If  an  engine  should  be  so  high  as  to  interfere 
with  the  travel  of  the  lower  cranes,  it  will  be  necessary  to 
see  that  there  is  a crane  set  on  each  side  of  the  engine  before 
cylinders  are  put  up,  so  as  not  to  cut  off  the  rest  of  the 
erecting  floor  from  the  crane  service  during  the  time  that 
the  high  engine  is  in  the  shop.  One  advantage  of  having 
light  quick-motion  traveling  cranes  placed  well  above  the 
heavier  cranes  is  that  the  upper  cranes  can  take  light  pieces 
and  lift  them  above  the  lower  cranes  and  carry  them  to  any 
place  on  the  erecting  floor  without  interfering  with  the 
heavy  work  of  the  larger  cranes. 

All  floors  on  which  erecting  is  done  should  be  firm 
and  solid,  so  that  there  is  no  danger  of  the  work  being 
thrown  out  of  line  by  settling  when  heavy  parts  are  added. 
Before  beginning  work,  the  erecting  floor  should  be  cleared 
of  all  unnecessary  obstructions  and  swept.  The  influence 
of  the  style  of  engine  on  the  manner  of  erection  will  be 
brought  out  in  the  description  of  the  three  principal  types 
of  horizontal,  vertical,  and  locomotive  engines.  For  the 
erection  of  small  engines  an  iron-plate  erecting  floor  on 
which  the  engine  can  be  bolted  down  and  tested  is  a great 
convenience. 


ERECTION  OF  A HORIZONTAL  STATIONARY 

ENGINE. 

40.  Preparation  of  tlie  Engine  Heel. — Before  the 
engine  bed  is  brought  to  the  erecting  floor  it  should  be 
machined  as  far  as  possible,  including  the  boring  of  the  main 
bearing,  if  this  is  cast  with  the  bed,  and  the  scraping  of  the 
guides.  The  guides  are  usually  scraped  to  a special  surface 
plate,  or  in  some  cases  to  the  crosshead  itself,  before  the 


28 


ERECTING. 


§23 


work  is  brought  to  the  erect- 
ing floor.  The  method  of 
erecting  a horizontal  engine 
is  not  influenced  greatly  by 
the  type  of  engine;  that  is, 
the  work  of  erecting  both 
Corliss  and  slide-valve  en- 
gines is  very  similar.  It  is 
best  to  carefully  level  up  the 
bed  on  the  erecting  floor. 
This  may  be  done  by  placing 
levels  on  the  guides  and  in 
the  pillow-block  bearings. 

41.  Fitting  tlie  Main 
Bearing  and  Cylinder  to 
the  Bed. — In  case  the  main 
bearing  is  cast  separately 
from  the  bed  and  attached  by 
bolts,  it  is  necessary  to  bring 
it  approximately  square  with 
the  bed.  This  may  be  ac- 
complished by  placing  a line 
through  the  crosshead  guides 
and  another  one  through  the 
pillow-block  and  testing  them 
to  see  that  they  are  at  right 
angles.  This  method  will 
only  set  the  bearing  approx- 
imately square  with  the  bed, 
though  it  will  usually  set  it 
so  nearly  square  that  any 
further  adjustment  can  be 
made  by  scraping  the  shaft 
bearing.  The  bed  with  the 
pillow-block  attached  should 
be  carefully  leveled  by  means 
of  leveling  jacks  or  wedges. 


ERECTING. 


29 


§23 

The  cylinder  is  bolted  to  the  bed  or  frame  and  a line  or 
wire  fastened  to  a piece  of  wood  bolted  to  one  of  the  studs 
in  the  end  of  the  cylinder,  as  shown  at  a , Fig.  14.  This  line 
is  carried  through  the  cylinder,  piston-rod  stuffingbox,  and 
guides,  and  fastened  to  the  end  of  the  frame  in  case  the 
pillow-block  is  cast  solid  with  the  frame;  or  in  the  case  of 
an  engine  in  which  the  pillow-block  is  bolted  to  the  frame, 
the  line  may  be  fastened  to  any  suitable  object,  as,  for 
instance,  the  angle  plate  and  stick  shown  at  b , Fig.  14.  The 
line  should  be  set  central  with  the  bore  of  the  cylinder  at 
the  back  end  by  calipering  from  the  inside  of  the  cylinder 
to  the  line.  This  may  be  done  \yith  an  inside  adjustable 
gauge  or  micrometer,  but  in  most  cases  it  is  better  to  use 
a light  pine  stick  like  that  shown  in  Fig.  15.  The  stick  a 


Fig.  15. 


is  tapered  at  both  ends  and  may  have  a pin  b driven  in  at 
each  end.  The  advantages  of  the  stick  in  calipering  are 
that  it  is  lighter  than  the  inside  micrometer  and  is  not 
affected  by  expansion  and  contraction  as  much  as  a metal 
gauge  would  be. 

The  line  must  also  be  brought  central  with  the  stuffingbox 
at  the  other  end  of  the  cylinder.  This  may  be  done  by 
means  of  a stick  similar  to  that  shown 
in  Fig.  15,  but  it  may  be  done  more 
quickly  by  means  of  the  device  shown 
in  Fig.  16.  This  consists  of  a hard-  c 
wood  block  a,  which  is  turned  to  just 
fit  the  stuffingbox  and  has  a |--inch 
hole  b drilled  in  the  center.  The  face 
of  the  block  is  turned  square  with  the 
outside,  and  two  center  lines  c d and  e f are  drawn  across 
the  face  at  right  angles  to  each  other.  By  sighting  along 
the  lines  cd  and  ef,  it  is  easy  to  determine  when  the  line  or 
wire  c d,  Fig.  14,  is  central  with  the  stuffingbox. 


30 


ERECTING. 


§ 23 


42.  Lining  the  Guides  to  the  Cylinder. — After 
this  the  guides  may  be  lined  to  the  cylinder  by  measuring 
from  the  inside  of  the  guides  to  the  line  at  the  top  and  bot- 
tom, as  at  f,  Figs.  14  and  16,  which  will  determine  whether 
the  line  is  central  to  the  guides  in  a vertical  plane.  This 
test  should  be  made  at  each  end  of  the  guides.  In  order  to 
see  whether  or  not  the  line  is  central  horizontally,  spots  g, 
Fig.  14,  are  cast  on  the  frame  and  faced  off  by  the  boring 
tool  at  the  same  time  that  the  guides  are  bored. 

Another  and  quicker  method  of  lining  the  guides  with  the 
cylinder  is  to  use  special  devices  similar  to  that  illustrated 
in  Fig.  17.  This  consists  of  a casting  a that  is  turned  to  fit 


the  inside  of  the  guides.  At  the  center  there  is  a small 
hole  b through  which  the  line  passes,  and  the  lines  c d and 
e f drawn  at  right  angles  to  each  other  serve  to  locate  the 
center  line  in  its  proper  position,  this  being  done  in  a 
manner  similar  to  that  described  in  Art.  41.  When  the 
device  shown  in  Fig.  17  is  used,  the  spotting  plates^*,  Fig.  14, 
are  not  necessary. 

43.  Bringing  the  Cylinder  in  Line  Witli  the 
Guides. — If  it  is  found  that  the  cylinder  is  not  in  line  with 
the  guides,  it  is  necessary  to  fit  the  joint  between  the  cylin- 
der and  guides  so  as  to  bring  them  in  line.  The  amount  of 


ERECTING. 


31 


§ 23 

adjustment  necessary  may  be  determined  by  slacking  off  the 
nuts  on  one  side  and  introducing  pieces  of  sheet  metal  until 
the  cylinder  and  guides  are  brought  into  exact  alinement. 
After  this  an  amount  equal  to  the  thickness  of  the  metal 
introduced  may  be  removed  from  the  other  side  of  the  end 
of  the  cylinder  or  guides.  Where  this  amount  is  very  small, 
it  is  sometimes  removed  by  filing  or  scraping;  when  it  is 
greater,  by  machining. 

It  has  been  found  practically  impossible  to  machine  parts 
so  accurately  that  the  cylinder  of  a large  engine  can  be 
brought  in  line  with  the  guides  without  fitting,  and  on  this 
account  many  manufacturers  place  a loose  ring  or  spacing 
piece  between  the  cylinder  and  the  guides,  and  in  the  case 
of  a tandem  compound  engine,  between  the  high-pressure 
and  low-pressure  cylinders.  After  the  amount  of  adjust- 
ment necessary  has  been  determined,  this  distance  piece  is 
taken  out  and  the  proper  amount  removed  from  the  high 
side. , When  this  method  is  followed,  care  must  be  taken  to 
mark  the  distance  piece  so  that  it  cannot  be  placed  in  a 
wrong  position.  To  insure  this,  it  is  well  to  have  at  least  one 
of  the  stud  or  bolt  holes  uniting  the  parts  not  located  accord- 
ing to  the  regular  spacing  system,  so  that  it  will  be  impos- 
sible to  put  the  castings  together  in  any  but  the  correct 
position.  This  may  also  be  accomplished  by  using  guides  or 
dowel-pins. 

Many  engine  builders  bore  all  their  cylinders  and  guides 
in  a vertical  boring  mill  and  so  reduce  the  difficulty  of  fitting 
the  parts,  but  in  the  case  of  a horizontal  engine,  the  parts 
will  spring  out  of  round  when  placed  in  a horizontal  position. 

44.  Fitting  the  Crank-Shaft. — After  the  cylinder 
and  guides  have  been  brought  into  perfect  alinement,  the 
crank-shaft  must  be  fitted.  The  outboard  bearing  may  be 
located  by  stretching  a line  through  the  shaft  bearings  at 
right  angles  to  the  lines  through  the  cylinder  and  guides. 
This  will  serve  to  locate  the  outboard  bearing  very  closely. 
After  this  has  been  done,  the  journals  of  the  shaft  should 
be  wiped  clean  and  given  a coat  of  marking  material.  The 


32 


ERECTING. 


23 


shaft  should  then  be  placed  in  its  bearings  with  the  lower 
half  of  the  boxes  in  position  and  given  a few  revolutions. 
The  shaft  is  then  lifted  out  of  the  bearings  and  the  high 
spots  scraped  off  with  a half-round  scraper.  This  operation 
is  repeated  until  the  shaft  shows  a good  bearing  in  both  the 
main  pillow-block  and  the  outboard  bearing.  After  the 
lower  half  of  each  box  is  scraped,  the  upper  halves  may  be 
put  in  place  and  fitted  in  like  manner.  The  shaft  is  then 
taken  from  the  bearings  and  the  cranks  pressed  or  shrunk  on 
and  keyed.  The  eccentrics  and  governor-driving  device 
are  also  placed  in  position,  after  which  tffe  shaft  is  returned 
to  its  place. 

In  order  to  make  sure  that  the  crank-shaft  is  exactly  at 
right  angles  to  the  center  line  of  the  engine,  and  that  it  is 


also  horizontal,  the  following  course  may  be  pursued:  The 
crankpin  a , Fig.  18,  is  brought  up  to  the  center  line  c d of 
the  engine  and  a piece  of  wood  b is  fitted  between  the  face 
of  the  crank  e and  the  head  of  the  crankpin  f.  A mark  is 
made  on  this  piece  of  wood  in  the  middle,  and  this  mark 
should  coincide  with  the  line  c d.  If  they  do  not  coincide, 
the  outer  end  must  be  moved  until  they  do.  The  shaft 
is  now  given  a half  revolution  to  bring  the  crankpin  under 
the  line  at  the  other  end  of  its  travel,  as  shown  by  the 
dotted  lines  at  a' . If  the  line  on  the  stick  b again  coincides 
with  the  center  line  c d,  the  shaft  is  at  right  angles  to  the 
center  line  of  the  engine.  In  order  to  test  the  shaft  to  see 
whether  it  is  level  or  not,  a fine  plumb-line  may  be  hung 


ERECTING. 


33 


§23 

vertically  before  the  shaft  and  the  crankpin  a brought  in 
contact  with  it  at  the  upper  portion  of  its  revolution,  and 
then  tested  again  at  the  bottom  of  the  revolution.  If  the 
crankpin  just  touches  the  line  at  both  the  top  and  the 
bottom,  the  shaft  is  horizontal. 

45.  Fitting  the  Reciprocating  Parts. — After  the 
engine  is  lined  up  and  the  shaft  square  and  level,  the  recip- 
rocating parts  may  be  put  in  place.  The  piston,  with  its 
piston  rod  attached,  is  slipped  into  the  cylinder  and  the 
crosshead  into  the  end  of  the  guides.  The  piston  rod  passes 
through  the  bushing  in  the  head  of  the  cylinder  and  is 
secured  to  the  crosshead.  These  parts  should  be  tested  as 
they  are  put  in  place,  to  see  that  they  line  up  properly. 
Some  makers  use  a crosshead  of  such  a pattern  that  the 
line  c d,  Fig.  14,  may  be  carried  through  the  crosshead  and 
used  in  testing  the  crosshead  to  see  that  it  lines  up  prop- 
erly. After  the  crosshead  and  piston  rod  are  in  place,  the 
connecting-rod  may  be  put  on.  Before  any  of  the  surfaces 
that  are  to  slide  or  move  on  one  another  are  placed  in  con- 
tact, care  should  be  taken  to  see  that  they  are  well  oiled. 
The  oiling  devices  are  put  in  place  as  fast  as  the  parts  are 
ready  for  them. 

The  control  of  the  movements  of  the  engine  depends  on 
the  governor;  consequently,  great  care  should  be  taken  to 
see  that  there  is  no  danger  whatever  of  the  governor  stick- 
ing or  failing  to  act.  In  order  to  insure  this,  the  governor 
should  be  assembled  separately  and  belted  up  so  as  to  run  at 
about  its  normal  speed.  The  gears  should  be  fitted  so  as  to 
run  as  quietly  and  as  smoothly  as  possible,  and  the  dashpots, 
weights,  and  all  parts  properly  adjusted  during  this  prelim- 
inary run.  It  is  usually  best  to  run  the  governor  one  or 
two  days  in  this  way.  After  the  governor  has  been  fully 
adjusted,  it  may  be  taken  down  and  placed  on  the  engine. 
If  the  engine  is  a Corliss  engine,  the  dashpots  are  responsi- 
ble for  the  closing  of  the  valves,  and  hence  they  should  be 
assembled  and  tested  before  being  placed  on  the  engine. 
Shops  building  this  class  of  engines  usually  have  some 

C.  S.  III.— 22 


ERECTING. 


34 


§ 23 


device  in  which  they  can  place  a dashpot  and  run  it  for 
some  time  while  adjusting  it.  After  the  dashpots  are  fully 
adjusted  they  are  placed  on  the  engine. 

4(3.  Oiling  Devices  and  Other  Small  Parts. — The 

oiling  devices  for  the  crankpin,  eccentrics,  crosshead,  gov- 
ernor, and  all  other  parts  are  put  in  place  as  fast  as  the 
parts  are  ready  to  receive  them  and  they  should  all  be 
tested  before  steam  is  let  into  the  engine. 

47.  I itti  ng  the  Flywheel. — Flywheels  for  small 
engines  are  made  either  solid  or  in  halves.  If  the  flywheel 
is  made  solid,  it  must  be  placed  on  the  crank-shaft  before 
this  is  lowered  into  the  bearings.  In  some  cases  there  is  not 
room  in  the  shop  to  put  the  flywheel  in  position,  and  hence 
the  engine  is  assembled  without  the  flywheel  being  placed  on 
the  shaft.  Where  it  is  possible,  it  is  best  to  erect  the  fly- 
wheel with  the  engine.  In  erecting  a large  built-up  flywheel, 
the  hubs  and  hub  flanges  are  placed  on  the  shaft  first.  The 
arms  and  segments  of  the  rim  are  then  attached  one  at  a 
time.  By  beginning  the  work  on  one  side,  the  arms  and 
sections  of  the  rim  may  be  attached  to  the  hub  flanges  near 
the  floor  level,  thus  doing  away  with  the  necessity  of  raising 
them  to  any  great  height.  After  one  arm  and  section  of 
the  rim  are  put  in  place,  they  may  be  lowered  into  the  pit 
and  the  next  one  in  order  connected.  This  process  may  be 
continued  until  the  wheel  is  completed.  When  the  work  is 
done  under  a traveling  crane,  it  is  usually  more  convenient  to 
place  each  of  the  arms  and  segments  at  the  top  of  the  wheel 
and  then  lower  them  far  enough  to  make  room  for  the  next. 

48.  Use  of  Dowel-Pins. — Whenever  it  is  necessary  to 
make  the  bed  of  an  engine  in  sections,  or  whenever  there 
arg  any  parts  that  require  accurate  alinement,  they  should 
be  doweled  together  This  is  done  by  drilling  holes  through 
the  pieces  and  reaming  them  out  with  a taper  reamer  after 
the  work  is  erected.  After  the  holes  are  drilled  and  reamed, 
taper  pins  are  fitted  to  them.  These  pins  are  usually  given 
a taper  of  from  £ to  J inch  per  foot.  As  each  part  is  put 
in  place,  it  should  be  clearly  and  distinctly  marked  by 


ERECTING. 


35 


§ 23 


letters,  figures,  and  lines,  so  that  it  may  be  easily  returned 
to  its  position  when  erecting  in  the  field.  If  the  work  is 
complicated,  it  is  well  to  keep  a record  of  the  marks  used 
so  as  to  avoid  confusion  in  the  final  erecting. 


49.  Lagging* — When  the  cylinder  attachments  have 
all  been  put  in  place  and  the  cylinder  tested,  the  jacket  or 
lagging  is  put  on.  This,  in  the  case  of  small  engines,  may 
consist  simply  of  a sheet  of  Russian  iron  cut  to  the  proper 
form,  bent,  and  screwed  to  the  flanges  of  the  cylinder.  In 
the  case  of  large  engines,  a framework  of  flat  or  angle  iron 
is  fitted  to  the  cylinder  and  wooden  strips  or  sheet-steel 
lagging  fitted  to  this  framework.  If  the  lagging  is  com- 
posed of  iron  or  steel,  it  is  put  in  place  by  a machinist,  while 
if  it  is  made  of  wood,  a carpenter  or  patternmaker  is  called 
on  to  do  the  fitting. 

50.  Placing  the  Engine  on  Dead  Center. — It  is 

often  necessary  to  place  the  crank  on  the  dead  center  when 
setting  the  valve,  and  this  is  done  in  the  following  manner: 
The  crank  is  turned  so  that  the  connecting-rod  will  stand 


in  the  position  shown  by  the  full  lines  a , Fig.  19,  and  a 
line  b is  drawn  on  the  crosshead  and  guide.  A scriber  or 
tram  similar  to  that  shown  in  Fig.  20  should  be  placed  in  a 
prick  mark  c on  the  bed,  and  a 
line  g drawn  on  the  crank.  The 
crank  should  now  be  rotated  so 
as  to  bring  the  rod  into  the  posi- 
tion shown  by  the  dotted  lines  c,  and  when  the  lines  b on  the 
crosshead  and  guide  coincide,  another  line  d is  drawn  on 
the  crank.  The  distance  from  g to  d may  be  bisected  with 


fig.  so. 


30 


ERECTING. 


§23 


a pair  of  dividers,  which  will  give  the  line  yon  the  crank, 
and  when  this  line  is  set  to  the  tram,  the  engine  is  on  the 
dead  center.  This  operation  may  be  repeated  when  it  is 
desirable  to  get  the  dead  center  on  the  other  end.  If  the 
crank  is  of  such  form  that  it  is  not  convenient  to  use  it  in 
this  manner,  the  flywheel  may  be  used  instead. 


51.  Valve  Setting. — No  definite  rule  can  be  given  for 
setting  the  valves  of  steam  engines,  as  the  work  is  largely  a 
matter  of  judgment.  The  valves  and  valve  gear  are  designed 
in  the  drawing  room,  and  the  details  are  worked  out  in  the 
machine  shop  according  to  the  drawings,  which,  in  the  case 
of  complicated  valve  gears,  give  full  directions  for  setting 
them.  The  slide  valve  is  the  one  most  commonly  met,  and 
a description  of  the  manner  of  setting  this  will  be  given. 

As  a valve  gear  is  generally  constructed,  there  are  two  ways 
of  adjustment  provided.  The  first  consists  of  a change  in 
the  length  of  the  valve  stem  and  the  second  consists  in  rota- 
ting the  eccentric  on  the  shaft.  By  altering  the  length  of 
the  valve  stem,  the  valve  may  be  made  to  travel  equally  each 
way  from  mid-position;  that  is,  if  the  valve  travels  \ inch 
too  far  toward  the  head  end,  shortening  the  stem  half 
that  amount  pulls  the  valve  \ inch  nearer  the  crank  and 
makes  it  travel  equal  each  way,  and  any  movement  of  the 
eccentric  hastens  or  retards  the  valve  action  as  it  may  be 
moved  ahead  or  back. 

The  valve  must  be  made  to  move  centrally  by  adjusting 
the  valve  stem  and  at  the  right  time,  by  moving  the  eccentric. 
To  accomplish  this,  set  the  crank  on  one  of  the  dead  points 
and  set  the  eccentric  so  as  to  give  as  nearly  the  proper  angle 
of  advance  as  can  be  judged.  The  lead  may  now  be  meas- 
ured and  the  crank  set  on  the  other  dead  point  and  another 
measurement  of  the  lead  made.  The  valve  may  now  be 
moved  half  the  difference  of  the  two  leads  and  be  given  the 
correct  lead  by  moving  the  eccentric,  which  should  bring 
the  lead  the  same  at  each  end.  No  general  method  can  be 
given  for  the  detailed  setting  of  all  forms  of  valves,  as  this 
depends  largely  on  the  design. 


§23 


ERECTING. 


37 


52.  Painting  and  Finishing. — All  rough  places  on 
the  bed  are  smoothed  off  by  chipping  and  filing  before 
painting,  or  in  some  cases  the  bed  is  given  a coating  of 
filling  material  that  fills  all  depressions.  After  the  bed  has 
been  filled  and  rubbed  down  with  sandstone  or  sandpaper,  it 
is  painted.  In  some  cases  the  specifications  call  for  the 
testing  and  acceptance  of  the  engine  before  painting. 

53.  Dismantling  the  Engine. — When  the  work  is 
passed  or  pronounced  correct  by  the  superintendent  or 
inspector,  the  man  that  has  had  charge  of  the  erection  of  the 
engine  oversees  the  taking  down  and  prepares  the  parts 
for  shipment.  The  lagging  is  usually  removed  and  boxed. 
All  small  parts  are  also  boxed.  These  boxes  should  be  num- 
bered and  a careful  record  kept  of  their  contents.  The 
cylinder,  in  the  case  of  large  engines,  is  mounted  on  skids. 
In  some  cases  the  cylinder  is  covered  with  non-conducting 
material,  so  as  to  prevent  the  radiation  of  heat  when  the 
lagging  is  in  place.  This  non-conducting  covering  may  be 
applied  in  the  shop  previous  to  shipment,  or  may  be  applied 
in  the  field.  All  finished  parts  of  the  work  are  given  a 
coating  of  some  protective  material  that  will  prevent  rust- 
ing. The  bearings  or  fitted  surfaces  are  boxed  or  covered 
with  boards  to  protect  them  from  injury.  Crankpins  and 
main  shafts  are  sometimes  wrapped  with  burlap  or  rope, 
and  if  large  and  finely  finished,  they  may  be  lagged  with 
wooden  strips.  In  the  case  of  comparatively  small  engines, 
the  entire  engine  is  sometimes  placed  on  skids.  In  case  the 
machinery  is  to  be  shipped  by  rail,  care  should  be  taken  to 
see  that  the  heavy  parts  of  the  load  come  over  the  trucks, 
the  lighter  parts,  boxes,  etc.  being  located  near  the  center 
of  the  car.  All  parts  should  be  securely  fastened,  so  that 
they  cannot  shift  during  shipment. 

54.  Foundation-Bolt  Templet. — While  the  engine 
is  being  erected  in  the  shop,  a templet  for  locating  the 
anchor  bolts  in  the  foundation  is  made.  This  templet 
should  include  the  correct  location  of  all  bolts  for  securing 
the  engine  bed,  cylinders,  and  outboard  bearing  to  the 


38 


ERECTING. 


§23 


foundation,  and  in  the  case  of  a large  and  complicated  plant 
like  a hoisting  engine,  should  also  include  the  bolts  for  the 
steam  brake,  steam  reverse,  drum-shaft  bearings,  etc.  The 
templet  is  usually  laid  out  from  the  drawing,  after  which  ali 
the  dimensions  should  be  checked  by  actual  measurements 
of  castings,  in  order  to  see  that  there  is  no  discrepancy 
between  the  drawing  and  the  casting.  After  the  holes  have 


been  properly  laid  out,  they  are  bored  the  same  size  as  the 
anchor  bolts.  This  templet  is  usually  made  of  1-inch  white- 
pine  lumber  and  must  be  thoroughly  braced.  The  parts 
should  be  put  together  in  a substantial  manner  with  screws 
or  bolts,  or  both,  and  also  marked  so  that  after  being  taken 
apart  for  packing  and  shipment,  the  templet  can  be  easily 
and  accurately  assembled  at  the  foundation  pit.  Fig.  21 
shows  a plan  of  such  a templet. 


ERECTION  OF  ENGINE  ON  FOUNDATION. 

55.  Foundations. — The  foundations  may  be  composed 
of  masonry,  brick,  or  concrete.  Stone  and  brick  should  be 
laid  in  good  cement  mortar.  The  bolts  may  be  built  into 
the  foundation  or  pockets  may  be  left  at  the  bottom  for  the 
washers  and  nuts,  and  holes  left  for  introducing  the  bolts 
later.  In  some  cases,  these  holes  may  be  made  by  building 
wooden  boxes  or  iron  pipe  into  the  foundation.  In  still 
other  cases,  the  foundations  are  built  with  pockets  near  the 


ERECTING. 


39 


§23 


bottom,  and  then  the  masonry  or  concrete  built  up  solid, 
after  which  the  bolt  holes  are  drilled  with  a diamond  drill. 
When  the  foundation  is  made  of  concrete,  it  is  usually 
better  to  build  the  bolts  into  the  foundation.  In  small  work 
a bunch  of  burlap  may  be  wrapped  around  each  bolt  and 
these  bunches  are  then  raised  along  the  bolts  as  the  brick- 
work or  masonry  progresses,  thus  leaving  clearance  spaces 
around  the  bolts. 

The  anchor  bolts  may  be  held  down  in  a variety  of  ways. 
Sometimes  a large  washer  is  placed  on  the  lower  end  of 
each  bolt.  In  other  cases  a stirrup  is  formed  at  the  lower 
ends  of  the  bolts  and  pieces  of  railroad  iron  passed  through 
these,  as  shown  at  #,  Fig.  22.  The  pieces  of  iron  may  be 
long  enough  to  extend  through  the  stirrups  of  two  or  more 
bolts  at  once.  The  foundation-bolt  templet  b , Fig.  22,  is 


supported  on  suitable  blocking  in  a level  position  and  rigidly 
braced  to  support  the  bolts.  Sometimes  it  is  necessary  and 
best  to  suspend  the  templet  by  braces  from  overhead  sup- 
ports. The  rails  a should  be  wedged  against  the  bottom 
of  the  stirrups  c by  driving  wedges  on  top,  as  shown  at  d. 
In  order  to  allow  some  adjustment  of  the  bolts,  a piece  of 
pipe  may  be  placed  about  them,  as  shown  at  e. 

56.  Appliances  for  Erecting  tlie  Engine  on  the 
Foundation. — The  engine  is  sometimes  erected  on  the  foun- 
dation by  the  same  man  that  did  the  erecting  in  the  shop. 
In  the  shop,  the  erector  has  the  advantage  of  all  the 
shop  tools  and  appliances,  including  cranes,  special  tools, 
etc.  When  the  engine  is  shipped  from  the  works,  the  man 
that  is  to  go  with  it  selects  such  tools  as  he  requires.  The 


b 


Fig.  22. 


40 


ERECTING. 


23 


tools  needed  vary  greatly  with  the  work  and  with  the  locality 
in  which  the  engine  is  to  be  erected.  Most  modern  power 
houses  have  traveling  cranes  in  the  engine  rooms  that  can 
be  used  in  erecting  the  engine  or  for  any  future  repair  work. 
In  this  case  very  few  tools  will  be  required.  If  the  engine 
is  to  go  into  a region  a long  distance  from  any  shop,  as,  for 
instance,  a mining  camp,  the  erector  must  take  practically 
everything  with  him  that  he  will  require.  Usually  one  or 
two  hydraulic  or  stone  jacks,  a few  screw  jacks,  and  some 
pinch  bars  will  be  all  of  the  larger  tools  necessary,  and,  in 
addition  to  this,  a liberal  stock  of  heavy  ropes,  wrenches, 
hammers,  chisels,  and  other  tools  that  may  be  necessary 
should  be  taken.  All  the  small  tools,  together  with  supplies, 
waste,  oil,  etc.,  should  be  kept  in  locked  tool  chests.  In 
case  heavy  parts  have  to  be  hoisted  some  distance,  it  maybe 
necessary  to  take  a chain  block  or  a hand  windlass,  crab,  or 
winch,  to  be  used  in  connection  with  a block  and  tackle. 
Sometimes  it  is  convenient  to  take  a stock  of  rollers  and 
blocking,  but  usually  these  can  be  obtained  in  the  field. 

57.  Setting  Engine  on  Foundation. — The  engine 
bed  and  cylinder  are  placed  on  the  foundation  and  bolted 
together.  All  the  dowel-pins  are  fitted  and  the  engine  is 
lined  up  by  stretching  a line  through  the  cylinder  and 
beyond  the  crank,  just  as  was  done  in  the  shop.  The 
engine  can  be  supported  on  iron  wedges  during  this  opera- 
tion. The  outboard  bearing  can  be  put  in  place  and  squared 
by  means  of  the  crank,  as  described  in  Art.  44.  After  the 
bedplate  is  properly  located  over  the  anchor  bolts,  the  clear- 
ance spaces  left  around  the  bolts  in  the  masonry  should  be 
filled  with  cement.  This  is  mixed  the  same  as  that  used 
under  the  engine  bed,  as  noted  below.  Enough  water  is 
added  to  the  cement  mixture  so  that  it  will  flow  readily  into 
the  holes.  In  large  work  with  removable  bolts,  the  cement- 
ing is  not  required.  After  the  engine  has  been  bolted  together 
and  lined  up,  the  space  between  the  bottom  of  the  bedplate 
and  the  foundation  may  be  filled  with  some  suitable  com- 
pound. In  some  cases  melted  sulphur  is  used,  in  others  a 


ERECTING. 


41 


§ 23 

mixture  of  iron  chips  and  sal  ammoniac  is  rammed  in  with  a 
calking  chisel,  while  in  still  other  cases  Portland  cement 
mixed  in  a proportion  of  1 part  cement  to  2 parts  sand  is 
employed.  When  the  cement  has  hardened,  the  flywheel  or 
pulley  may  be  put  in  place  and  the  caps  over  the  bearings 
adjusted.  All  parts  that  are  subjected  to  friction  should  be 
thoroughly  oiled  before  being  put  into  place,  as  an  unoiled 
surface  sometimes  cuts  during  the  first  few  revolutions  before 
the  oil  reaches  it  through  the  oil  hole.  The  piston,  cross- 
head, connecting-rod,  cylinder  head,  governor,  valve  gear, 
oiling  devices,  lagging,  and  piping  are  assembled  in  the 
order  named. 

The  engine  may  now  be  turned  a full  revolution  by  hand 
to  make  sure  that  all  is  clear.  Next,  care  should  be  taken 
to  see  that  everything  is  in  adjustment;  then  the  steam  may 
be  turned  on  and  the  engine  started  very  slowly.  After 
the  engine  is  started  with  steam,  a thorough  inspection  of 
all  working  parts  should  be  made  and  all  the  oiling  devices 
properly  adjusted.  Any  parts  that  have  been  left  too  loose 
may  now  be  tightened  to  proper  running  fits,  and  any  part 
that  shows  a tendency  to  heat  should  be  examined  and 
adjusted.  After  the  engine  has  been  running  at  full  speed 
for  some  time,  it  may  be  belted  up  and  kept  at  work  while 
the  indicator  test  is  being  made.  This  test  will  usually  show 
any  defect  in  adjustment  of  valve  setting,  which  may  be 
corrected  at  this  time. 


ERECTING  A VERTICAL  STATIONARY  ENGINE. 

58.  General  Consideration. — The  method  followed 
in  erecting  a vertical  engine  does  not  differ  materially  from 
that  used  in  the  horizontal  engine,  but  as  the  parts  are 
differently  arranged,  and  in  most  cases  some  additional 
parts  are  required,  a description  showing  the  principal 
points  of  difference  may  be  of  interest.  As  a rule,  it  is 
more  difficult  to  erect  a vertical  engine  without  the  aid  of 
cranes  or  hoists  than  a horizontal  engine.  Very  large 
horizontal  engines  are  frequently  erected  in  the  field  without 


42 


ERECTING. 


§23 


any  hoisting  tackle  whatever,  all  the  parts  being  moved 
on  rollers  and  lined  up  by  means  of  jack-screws.  In  the 
case  of  a vertical  engine,  it  is  usually  necessary  to  rig  a 
derrick,  shear  legs,  or  some  hoist  when  in  the  field. 

59.  Work  Necessary  on  the  Bed. — The  bed  a, 

Fig.  23,  is  leveled  by  means  of  wedges  or  erecting  jacks,  as 
in  the  case  of  a horizontal  engine.  The  bearings  for  the 
crank-shaft  may  be  scraped  either  before  or  after  the  guides 


fig.  23. 


are  in  place.  Sometimes,  to  aid  in  scraping  these  bearings, 
a hollow  cast-iron  shaft  is  made  of  the  same  diameter  as  the 
crank-shaft.  This  is  lighter  than  the  crank-shaft  and 
serves  as  a surface  plate  for  scraping  the  bearings  into  line. 

60.  Fitting  the  Guides  and  Cylinders. — The  frames 
and  guides  d and  d ' are  placed  on  the  bed  and  temporarily 
bolted  down.  A center  line  along  the  center  of  the  shaft  is 


§23 


ERECTING. 


43 


established  by  placing  blocks  across  the  bearings,  as  shown 
* at  e.  A piece  of  tin  is  fastened  to  the  center  of  each  one  of 
these  and  a center  line  marked  on  it.  A long  straightedge 
is  then  laid  across  both  blocks  and  a center  line  established. 
A line,  as  fghi,  is  stretched  through  each  cylinder.  The 
line  is  secured  at  the  bottom  to  a plank /,  which  is  blocked 
or  clamped  to  the  bottom  of  the  bedplate  and  has  a hole  in 
the  center  through  which  the  line  passes.  At  the  upper  end, 
above  the  cylinders,  the  line  is  secured  to  the  plank  k.  The 
line  passes  over  pulleys  at  g and  //,  and  is  kept  taut  by  a 
heavy  weight  at  i;  a piano  wire  capable  of  standing  a break- 
ing stress  of  400  pounds  is  usually  used  for  this  purpose, 
and  the  weight  at  i may  vary  from  100  to  200  pounds. 
This  weight  should  be  located  so  that  it  will  do  no  damage 
if  the  wire  should  break.  After  the  line  is  established,  the 
guides  and  cylinders  are  adjusted  to  it.  If  desired,  the 
weight  at  i may  be  hung  under  the  cylinders  in  place  of 
the  plank  f.  It  is  best  to  suspend  the  weight  in  a vessel  of 
water  to  prevent  vibration.  Great  care  must  be  taken  to 
see  that  the  lines  fg  and  f'g'  are  the  same  distance  apart, 
both  top  and  bottom,  and  are  in  the  same  vertical  plane. 

If  it  is  found  that  the  cylinder  does  not  come  in  line  with 
the  guides,  packing  pieces  must  be  placed  between  the 
cylinder  and  the  guides,  as  in  the  case  of  a horizontal 
engine,  after  which  a sufficient  amount  must  be  dressed 
from  the  end  of  the  cylinder  or  the  intermediate  piece, 
bringing  the  two  into  alinement.  In  measuring  from  the 
line  to  the  cylinders,  or  from  the  line  to  the  guides,  a 
wooden  measuring  piece  may  be  used,  as  described  in 
Art.  -41.  After  the  cylinders  and  guides  are  properly 
located,  they  are  securely  clamped,  in  place,  and  the  bolt 
holes  for  holding  the  uprights  to  the  bed,  the  guides  to  the 
uprights,  if  the  latter  are  made  separate,  and  the  cylinders 
to  the  guides,  are  reamed  ready  for  the  bolts,  and  the  holes 
for  the  dowel-pins  are  drilled  and  reamed  and  the  pins  fitted. 

61.  Placing  Reciprocating  Parts. — The  placing  of 
the  reciprocating  parts  of  vertical  engines  does  not  differ 


44 


ERECTING. 


23 


materially  from  that  of  horizontal  engines,  and  the  method 
of  squaring  the  crank-shaft  to  the  center  line  that  is  used  in 
the  horizontal  engine  can  also  be  employed  in  the  vertical 
engine. 

62.  Oiling  Devices  and  Smaller  Parts. — In  some 
cases,  vertical  engines  are  fitted  with  separate  oiling  devices 
for  each  bearing,  while  in  other  cases  an  oil  tank  is  arranged 
at  or  near  the  cylinder  from  which  pipes  lead  to  the  various 
bearings.  Another  system  provides  a reservoir  with  a pump, 
either  attached  to  the  engine  or  as  a separate  machine, 
which  distributes  the  oil  through  a suitable  arrangement  of 
piping.  All  these  devices  are  placed  in  position  during 
erection.  Owing  to  the  fact  that  many  parts  of  the  engine 
are  not  accessible  from  the  floor,  it  becomes  necessary  to 
provide  some  device  by  means  of  which  the  attendant  can 
reach  any  part  of  the  engine.  To  accomplish  this,  plat- 
forms or  floors  are  built  around  the  engine  at  different 
elevations.  These  platforms  are  usually  iron  plates  sup- 
ported on  brackets,  and  are  reached  by  staircases  leading 
from  the  floor  of  the  engine  room.  These  brackets  and 
plates  are  all  placed  in  position  as  the  various  parts  of  the 
engine  are  being  assembled.  In  the  outer  edge  of  the  plates, 
provision  is  made  for  standards,  which  carry  a hand  rail, 
usually  composed  of  a piece  of  brass  or  iron  pipe.  Large 
vertical  engines  are  often  provided  with  hand  or  similar 
turning  gear  for  turning  the  engine  around  a portion  of  a 
revolution  in  starting  or  when  fitting  belts.  They  are  also 
supplied  with  steam,  vacuum,  and  revolution  gauges,  and  a 
clock.  Provision  must  be  made  for  attaching  these  to  the 
engine  frame,  though  they  are  not  generally  assembled  in 
place  until  the  engine  is  erected  upon  its  foundation ; or 
they  may  be  erected  on  a board  entirely  separate  from  the 
engine.  Provision  must  also  be  made  on  all  engines  for 
attaching  the  steam  indicator. 

63.  Dismantling  Vertical  Engines.  — After  an 
engine  has  been  erected  and  tested,  it  is  dismantled  in  a 


46 


ERECTING. 


§23 


manner  similar  to  that  used  in  taking  down  large  horizontal 
engines,  except  that  it  must  be  done  to  a greater  extent. 

64.  Erecting  on  Foundation. — The  erection  of  a 
vertical  engine  on  the  foundation  does  not  differ  materially 
from  that  of  a horizontal  engine,  with  the  exception  of  the 
fact  that  in  some  cases  a line  is  not  stretched  through  the 
engine  when  it  is  erected  on  the  foundation.  When  no  line 
is  used,  bolts  and  dowel-pins  are  depended  on  entirely  for 
bringing  the  parts  into  line.  Care  must  be  taken  in  erect- 
ing a vertical  engine  to  see  that  the  bedplate  is  carefully 
leveled  and  has  a firm  bearing  before  the  other  heavy  parts 
are  assembled  on  it. 


LOCOMOTIVE  ERECTION. 


METHOD  BY  PLACING  THE  BOILER  FIRST. 

65.  Methods  of  Erection. — The  erection  of  locomo- 
tives varies  in  different  shops,  not  only  owing  to  the  different 
ideas  possessed  by  the  men  in  charge,  but  also  on  account 
of  the  varying  equipment  of  the  shops.  In  one  method  the 
locomotive  boiler  is  placed  first  and  all  the  parts  assembled 
about  it,  the  principal  argument  in  favor  of  this  method 
being  that  the  boiler  is  the  stiffest  thing  about  a locomotive 
engine,  and  hence  everything  should  be  lined  up  to  fit  it. 
In  the  other  method,  the  frames  and  working  parts  are 
erected  first  and  the  boiler  placed  on  them.  The  first 
method  will  be  now  considered. 

66.  Placing  the  Boiler.  — In  Fig.  24,  a locomotive 
boiler  is  shown  ready  for  assembling  the  other  parts  about 
it.  The  length  of  the  top  part  of  the  blocking  at  a under 
the  firebox  end  must  be  less  than  the  distance  between  the 
two  frames,  so  as  not  to  interfere  with  the  other  placing. 
The  barrel  or  shell  of  the  boiler  is  supported  by  a strong 
trestle  b that  rests  on  the  block  c.  It  is  not  necessary  that 
the  boiler  be  level  endwise,  but  care  should  be  taken  to  have 


§23 


ERECTING. 


47 


it  plumb  sidewise.  The  center  of  the  dome  d should  come 
over  the  center  line  of  the  bottom  of  the  firebox,  and  each 
side  of  the  barrel  of  the  boiler  should  be  equally  distant  from 
the  vertical  center  line.  Should  there  be  any  slight  dis- 
crepancies in  the  shape  of  the  boiler,  they  should  be  averaged 
in  the  setting.  In  other  words,  in  case  it  is  found  that  with 
the  center  of  the  dome  over  the  center  of  the  bottom  of  the 
firebox  the  barrel  of  the  boiler  projects  more  on  one  side  of 
the  vertical  line  than  on  the  other,  the  sides  of  the  boiler 
may  be  brought  equidistant,  or  nearly  so,  from  the  center 
of  the  bottom  of  the  firebox,  even  if  the  dome  is  thrown 
slightly  to  one  side. 

67.  Placing  the  Cylinders. — The  cylinders  are 
brought  under  the  boiler  and  approximately  to  their  places, 
the  saddle  a , Fig.  25,  being  in  contact  with  the  barrel  of  the 
boiler.  Lines  b and  b'  are  then  run  through  each  cylinder 
and  fastened  to  some  fixed  object,  as  the  post  d near  the 
back  of  the  firebox.  The  lines  b and  b'  should  be  parallel 
and  equidistant  from  the  sides  of  the  front  end  of  the  boiler 
shell,  as  shown  by  the  line  c , hung  over  the  top  of  the  boiler 
shell  and  having  the  weights  f attached  to  each  end.  The 
two  center  lines  are  brought  to  the  desired  distance,  plus 
the  amount  to  be  chipped  off  the  saddle,  below  the  firebox 
at  the  point  e.  This  is  accomplished  by  placing  a straight- 
edge under  the  firebox  at  e and  measuring  to  the  lines.  The 
horizontal  distance  from  the  sides  of  the  firebox  to  the  center 
lines  may  also  be  determined  and  made  equal  on  both  sides. 
The  erector  then  scribes  a chipping  line  all  around  the  saddle 
by  means  of  a pair  of  dividers  or  a small  surface  gauge. 
The  cylinders  are  next  moved  out  in  front  of  the  boiler  and 
the  saddle  chipped  to  the  line  referred  to.  The  cylinders 
are  then  returned  to  their  positions  in  contact  with  the 
boiler  shell  and  tested  by  the  lines.  In  some  cases  it  may 
be  necessary  to  remove  them  and  make  any  slight  corrections 
that  may  be  required  by  further  chipping  and  filing.  A 
narrow  chipping  strip  is  provided  all  the  way  around  the 
saddle  a to  facilitate  this  work  of  fitting. 


48 


ERECTING. 


§23 


Fig.  25. 


C.  S.  III.— 23 


Fig. 


50 


ERECTING. 


§23 


The  space  above  the  upper  surface  of  the  saddle  a and 
between  the  chipping  strips  is  then  filled  with  cement  to 
give  a solid  bearing  between  the  saddle  and  the  boiler. 
Different  materials  are  used  for  this  purpose,  as,  for  instance, 
asbestos,  stove  putty,  red  and  white  lead  cements  with  or 
without  iron  chips  incorporated  in  them,  and  in  some  cases 
iron  chips  and  sal  ammoniac  have  been  used  to  form  a rust 
joint.  In  all  cases  considerable  care  is  necessary  to  use  just 
the  right  amount  of  material,  on  account  of  the  fact  that 
there  is  no  chance  to  calk  or  drive  it  into  place.  After  the 
space  in  the  saddle  has  been  filled,  the  cylinders  are  bolted 
to  the  shell  and  blocking  placed  under  them  to  support  the 
weight  of  the  front  end  of  the  locomotive.  The  trestle  b , 
Fig.  24,  is  then  removed  from  under  the  barrel  of  the  boiler, 
as  it  would  be  in  the  way  during  the  latter  operation. 

G8.  Placing  the  Frames. — The  frames  are  next 
placed  in  position,  as  shown  in  Fig.  26.  They  are  bolted  to 
the  cylinders  at  the  front  end,  and  the  foot-plate  a is  bolted 
across  the  back  ends,  which  spaces  them  properly.  The 
waste  plate  b is  attached  to  the  frames,  but  not  to  the  barrel 
of  the  boiler.  The  guides  c and  d are  bolted  to  the  cylinders 
and  blocked  in  place.  In  Fig.  26  the  lower  guide  is  sup- 
ported by  a jack-screw  and  the  upper  one  by  blocking. 
While  this  work  has  been  in  progress  other  men  have  put 
in  the  tubes  and  dry  pipe,  drilling  and  tapping  the  holes  for 
the  gauge  cocks  and  cleaning  plug  holes,  also  the  holes  for 
the  studs  for  the  running-board  brackets,  sand  box  and 
bell,  the  combination  globe  or  steam  turret,  and  any  other 
holes  that  may  be  required. 

G9.  Lining  tlie  Guides. — The  guides  are  supported 
at  the  back  end  by  the  yoke  a , Fig.  27.  A line  b is  passed 
through  each  cylinder  to  a piece  of  board  held  in  one  of  the 
pedestals,  as  shown  at  c.  These  lines  are  centered  in  the 
front  ends  of  the  cylinders  and  in  the  piston-rod  glands  at 
the  back  ends.  After  the  lines  are  in  place,  the  guides  are 
set  parallel  to  the  lines  and  the  guide  yoke  adjusted.  About 
this  time  the  waste  sheet  d,  Fig.  27,  is  secured  to  the  barrel 


ERECTING. 


51 


§ *3 


Fig. 


52 


ERECTING. 


§23 


of  the  boiler  by  the  angle  e.  After  the  guides  and  guide 
yoke  are  in  place  the  yoke  is  secured  to  the  frames  by  proper 
attachments  and  to  the  boiler  by  a sheet  and  angle,  as  shown 
at  a , Fig.  28.  While  this  work  is  going  on  the  holes  for  the 
furnace  pads  (also  called  expansion  pads  or  bearers)  are 
drilled,  as  shown  at  f,  Fig.  27,  and  the  pads  and  links  put 
on,  as  shown  at  b and  c , Fig.  28.  At  the  same  time  other 
men  are  placing  other  details,  such  as  the  bell,  stack,  oil 
pipes,  etc.- 

70.  Testing  the  Boiler. — The  firing  or  testing  of  the 
boiler  in  some  shops  is  done  without  taking  the  engine  from 
the  erecting  floor.  A better  way  is  to  run  two  temporary 
trucks,  made  expressly  for  the  purpose,  under  the  locomo- 
tive, as  shown  at  d and  e , Fig.  28.  This  enables  it  to  be 
hauled  to  the  transfer  table  and  moved  to  the  firing  room. 
Locomotive  boilers  are  sometimes  tested  by  using  steam 
piped  to  them  from  a high-pressure  stationary  boiler  installed 
for  this  purpose,  but  the  better  practice  is  to  use  a fire  in 
the  firebox  of  the  boiler,  as  this  makes  the  test  under  actual 
working  conditions. 

The  boiler  is  first  filled  to  the  top  of  the  dome  with  hot 
water,  through  an  injector.  Any  leaks  that  may  appear 
are  tightened  by  calking,  and  a water  pressure  sufficiently 
high  is  slowly  applied.  In  ordinary  practice  this  is  about 
240  pounds.  While  the  pressure  is  on,  if  any  leaks  appear, 
they  are  marked  with  chalk.  The  pressure  is  then  taken 
off,  and  the  leaks  that  have  been  marked  are  carefully  calked. 
The  water  is  lowered  to  one  gauge  and  a fire  started  in  the 
firebox.  The  water  will  rise  to  two  gauges  by  expansion. 
Steam  is  raised  to  the  desired  pressure,  usually  equal  to  the 
water  pressure  used.  For  instance,  if  the  steam  pressure 
were  240  pounds  when  this  limit  had  been  reached,  the 
pressure  would  be  reduced  to  50  pounds,  which  process  is 
repeated  three  times.  The  oil  pipes  are  tested  at  the  same 
time  to  see  that  they  are  all  right  before  they  are  covered 
with  the  jackets.  The  jacket  is  not  placed  on  the  boiler 
until  the  engine  is  returned  to  the  erecting  shop  after  firing. 


Fig. 


Fig.  29. 


§23 


ERECTING. 


55 


71.  Placing  the  Wheels,  Valve  Gear,  and  Details. 

The  locomotive  is  now  brought  back  to  the  erecting  shop 
and  lifted  from  the  temporary  trucks  by  the  traveling  crane, 
and  is  ready  for  its  own  wheels  to  be  run  under  it,  including 
the  truck.  The  engine  is  then  lowered  into  place,  as  shown 
in  Fig.  29.  The  links  and  motion  work  are  next  put  up  and 
the  valves  set.  At  the  same  time  the  boiler  is  being  covered 
or  lagged  with  a non-conducting  material,  and  the  planished 
iron  jacket,  running  boards,  cab,  and  pilot  are  placed  in 
position.  The  running  boards,  cab,  and  pilot  are  made  in  a 
different  shop  and  brought  to  the  erecting  floor  ready  for 
placing. 

The  painters  have  been  following  the  machine  work  most 
of  the  time,  as  opportunity  offers.  The  cab,  sand  box,  and 
some  other  parts  are  painted  before  being  brought  to  the 
erecting  shop. 

To  enable  men  to  work  under. the  locomotive,  an  erecting 
pit  about  38  feet  long,  47  inches  wide,  and  32  inches  deep  is 
usually  provided  between  the  tracks  of  each  erecting  stall. 
This  pit  usually  begins  about  14  feet  from  the  door. 

The  tender  is  made  complete  in  another  department, 
and  is  ready  to  be  attached  to  the  locomotive  after  it 
is  run  out  from  the  erecting  shop. 


METHOD  OF  ERECTING  BY  PLACING  THE  CYLINDERS 
AND  FRAME  FIRST. 

72.  Placing  tlie  Cylinders  and  Frame. — In  this 
method  the  cylinders  are  first  placed  on  four  jack-screws, 
the  saddle  having  been  machined  to  the  same  radius  as  the 
smokebox.  The  frames,  guides  and  guide  yokes,  foot-plate, 
buffer  beam,  and  some  other  parts  are  put  in  place,  the 
cylinders  jacketed,  and  the  parts  adjusted  to  one  another. 
During  this  work  the  frames  are  supported  at  the  back  end 
by  jack-screws.  The  cylinders  are  brought  into  the  proper 
relation  to  the  frames  by  means  of  lines,  as  described  in  the 
other  method  of  erection. 


56 


ERECTING. 


23 


73.  Placing  tlie  Boiler. — After  the  frames  and  cylin- 
ders are  joined,  the  boiler  is  brought  by  the  traveling  crane 
and  lowered  to  its  place,  and  the  connections  between  the 
boiler,  frame,  and  cylinders  are  made.  If  the  boiler  is 
not  perfectly  round,  it  will  not  fit  the  saddles  perfectly. 
After  all  the  parts  that  have  been  erected  together  have  been 
attached  to  the  boiler,  the  entire  engine  is  lifted  by  a crane 
in  readiness  to  receive  the  wheels  that  are  now  rolled  under 
and  placed  in  their  proper  positions.  After  this  the  stack 
and  pilot  are  put  on,  the  boiler  tested,  lagged,  and  jack- 
eted, and  the  rods,  valve  work,  running  board,  cab,  fixtures, 
and  other  parts  are  put  in  place  very  much  as  in  the  first 
method  described. 

74.  Comparison  of  tlie  Two  Methods. — The  main 
difference  between  the  two  plans  described  is,  briefly,  as 
follows:  In  the  first  plan,  the  boiler  is  the  starting  point,  or 
backbone,  and  all  other  parts  are  built  around  it.  In  the 
last-mentioned  method,  the  main  part,  or  skeleton  of  the 
engine,  is  assembled  and  the  boiler  added,  after  which  the 
running  gear  and  the  remainder  of  the  engine  are  put  in 
place.  When  the  second  method  is  used,  no  erecting  pit  is 
required. 


SHOP  HINTS. 

(PART  1.) 


RIGGING. 


DEVICES  FOR  HOISTING  AND  MOVING. 


LIST  OF  APPLIANCES. 

1.  For  the  handling  of  heavy  pieces  of  machinery  in 
the  field,  or  in  buildings  where  they  are  to  be  erected, 
tools  and  appliances  known  by  the  general  name  of  rig- 
ging are  used.  The  appliances  ordinarily  required  are  the 
following: 

1.  The  winding  winch,  or  windlass,  which  is  a machine 
with  a rope  drum  and  appliances  for  turning  the  same. 

2.  A set  of  different  sized  tackles,  in  which  the  rope,  or 
line,  should  be  long  enough  to  reach  the  windlass  or  to  allow 
a number  ^of  men  to  grasp  it  when  the  blocks  are  the 
greatest  required  distance  apart. 

3.  One  or  more  screw  jacks  and  hydraulic  jacks  are  indis- 
pensable. 

4.  Slings  or  straps  made  of  rope  spliced  together  to  form 
an  endless  rope. 

§ 24 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


SHOP  HINTS. 


§24 


5.  Lashings,  these  being  pieces  of  rope  of  different  sizes 
and  lengths,  with  the  ends  stopped  up,  by  tying  or  binding, 
to  prevent  their  unraveling. 

6.  Blocks  of  wood,  rectangular  in  shape  and  of  different 
sizes,  and  timber  for  the  construction  of  derricks  and  gin 
poles. 

7.  Wedges,  both  of  iron  and  of  hard  wood. 

8.  Crowbars  and  pinch  bars. 

9.  Chains  and  chain  hoists. 

10.  Rollers,  which  are  generally  short  pieces  of  iron  pipe. 

The  articles  enumerated  in  the  first,  second,  third,  eighth, 
and  ninth  paragraphs  can  usually  be  bought  cheaper  and 
better  than  they  can  be  made.  Slings,  lashings,  blocks, 
wedges,  and  rollers  are  rarely  bought  in  the  market,  but  are 
usually  made. 


PINCH  BARS. 

2.  The  most  common  form  of  pinch  bar  is  a straight 
iron  or  steel  bar,  square  on  one  end,  with  a flat,  wedge- 
shaped  point  turned  slightly  to  one  side  and  the  other  end 
round  and  slightly  tapering  to  form  a handle,  as  shown  in 


Fig.  l. 

Fig.  1 (a).  This  form  of  bar  is  usually  about  4 feet  long, 
and  is  commonly  called  a crowbar.  The  smaller  pinch 
bars,  used  in  machine  shops  and  in  erecting  machinery,  are 


24 


SHOP  HINTS. 


3 


from  2 to  4 feet  long,  and  are  made  of  -f-inch  or  f-inch 
octagonal  steel,  as  shown  at  ( b ). 

A rather  convenient  form  of  pinch  bar  that  is  well  adapted 
for  lifting  and  moving  quite  heavy  weights  is  shown  in  (c). 
As  will  be  seen  by  referring  to  the  illustration,  the  bar  is 
mounted  on  two  wheels,  and  consequently,  when  the  bar 
supports  a heavy  weight,  the  bar  and  weight  can  be  easily 
shifted.  This  form  of  pinch  bar  is  sometimes  called  a 
cow  bar. 


USE  OF  SLINGS. 

3.  Slings  are  loops  of  rope  or  chain  used  for  attaching 
weights  to  the  hook  of  a tackle  or  for  fastening  a tackle  block 
to  some  support.  In  order  that  a 
sling  may  best  serve  its  purpose,  one 
of  several  methods  of  fastening  it  to 
the  block  has  to  be  chosen,  the 
choice  of  method  being  influenced  to 
some  extent  by  the  weight  of  the 
load  to  be  lifted.  For  instance,  the 
resistance  of  the  sling  is  least  if  used 
single,  as  shown  in  Fig.  2 (a),  but 
its  greatest  possible  strength  may  be 
obtained  by  looping  it  over  the  hook 
as  shown  in  Fig.  2 (b),  thus  increas- 
ing the  surface  of  the  sling  in  contact 
with  the  hook  of  the  tackle  block.  The  sling  may  be 
applied  to  the  piece  of  work  to  be  moved  in  the  same 
manner  in  which  it  is  fastened  to  the  hook  of  the  tackle 
block;  that  is,  it  may  be  either  passed  around  singly,  as 
in  Fig.  2 (a),  or  doubled,  as  in  Fig.  2 (6),  the  latter  method 
being  preferable  owing  to  the  absence  of  any  danger  from 
slipping  of  the  sli|ng.  It  is  obvious  that  if  the  sling  is  fas- 
tened by  doubling  over,  a noose  is  formed  and  the  sling 
is  thus  tightened  on  the  work  when  the  free  end  is 
pulled;  hence,  the  preference  of  riggers  for  this  half-hitch 
arrangement. 


(a)  (b) 

Fig.  2. 


4 


SHOP  HINTS. 


§ 24 


USE  OF  LASHINGS. 

4.  Where  headroom  is  limited,  the  tackle  may  be 
attached  to  the  work  by  means  of  lashing.  This  is  simply 


over  the  hook,  the  ends  of  the  line  being  fastened  by  a 
knot. 

Another  advantage  of  lashing  lies  in  the  fact  that  a small 
rope  may  be  used  ; the  necessary  strength  is  then  obtained 
by  increasing  the  number  of  turns. 


INSPECTING  ROPES,  SLINGS,  AND  LASHINGS. 

5.  There  will  come  a time  when,  from  repeated  use  and 
occasional  abuse,  the  strength  of  ropes,  slings,  and  lashings 
will  be  impaired;  in  order  to  prevent  any  accident  that  may 
occur  on  account  of  this  loss  of  the  strength,  it  is  necessary 
to  know  how  to  detect  a weakened  rope.  The  first  thing  to 
be  done  is  to  inspect  the  outside  carefully,  running  over  the 
lines  from  end  to  end,  and  noting  if  any  of  the  strands,  or 
yarns  composing  the  strands,  are  damaged.  If  nothing 
wrong  is  discovered  about  the  outside  of  the  rope,  the 
inside  should  be  inspected,  for  the  reason  that  a rope  will 


Fig.  3. 


a piece  of  rope  suffi- 
ciently long  to  admit 
of  its  being  passed 
several  times  around 
the  piece  to  be  moved. 
Work  is  fastened  to 
the  tackle  by  first 
bringing  the  back  of 
the  hook  of  the  tackle 
block  in  contact  with 
the  piece  to  be  hoisted, 
as  shown  in  Fig.  3,  and 
then  passing  several 
turns  of  the  line 
around  the  work  and 


§24 


SHOP  HINTS. 


5 


often  be  perfectly  sound  on  the  outside,  but  utterly  bad 
inside.  The  inside  may  be  inspected  by  taking  the  rope  in 
both  hands  and  untwisting  it  sufficiently  to  expose  the  inner 
surfaces  that  have  been  chafing  against  one  another.  Then, 
if  the  life  or  utility  of  the  line  has  been  impaired  by  long 
use,  a considerable  number  of  broken  fibers  will  be  found; 
if  in  a bad  state,  they  may  have  been  reduced  to  powder. 
If  broken  fibers  are  discovered,  the  use  of  the  rope  should 
be  confined  to  loads  not  heavier  than  half  the  load  it  for- 
merly could  stand;  if  a considerable  quantity  of  powder 
is  found,  the  line  should  be  condemned  at  once  as  unfit 
for  use. 

Slings  and  lashings,  as  a general  rule,  are  ruined  by  exter- 
nal chafing  received  when  moving  rough  castings,  etc.,  and 
hence  their  safety  can  be  determined  from  their  external 
appearance.  Ropes  or  lines,  on  the  other  hand,  when  used 
for  tackle  blocks,  receive  the  greatest  wear  on  the  inside, 
owing  to  the  chafing  and  grinding  of  the  strands  when 
passing  over  small  pulleys  under  heavy  strains. 


CHAIN  HOISTS. 

6.  Chain  hoists,  as  a general  rule,  are  best  adapted  to 
lifting  heavy  loads  where  the  help  available  is  scarce,  since, 
owing  to  the  way  in  which  they  are  geared,  they  require  very 
little  power.  There  is,  however,  a great  range  in  the  effi- 
ciency of  chain  blocks,  varying  from  18  per  cent,  with  the 
common  differential  chain  hoist , where  it  takes  considerable 
power  to  lower  the  load,  to  79  per  cent,  efficiency  in  the 
case  of  the  triplex  hoist.  One  great  advantage  of  chain 
hoists  lies  in  the  fact  that  they  may  be  stopped  at  any  point; 
that  is,  theToad  will  remain  in  a state  of  rest,  without  secur- 
ing the  chain  in  any  way,  until  set  in  motion  again  by  the 
operator.  With  a tackle  this  cannot  be  done,  since  it  is 
necessary  to  fasten  the  free  end  of  the  line  to  some  station- 
ary object  in  order  to  hold  the  load;  this,  of  course,  is  often 
a drawback  to  the  use  of  a tackle,  and  a great  point  in  favor 


6 


SHOP  HINTS. 


§ 24 

of  the  chain  hoists.  To  offset  this,  we  have  the  fact  that, 
with  long  usage,  the  iron  in  the  chain  links  becomes  crystal- 
lized, and  hence  is  liable  to  break  suddenly  even  under  a 
moderate  load.  The  effects  of  crystallization  can,  however, 
be  rem’edied  to  a large  extent  by  a thorough  annealing  of 
the  chain.  This  can  most  readily  be  done  by  coiling  the 
chain  after  removing  it  from  the  blocks,  and  then  building  a 
charcoal  fire  around  it.  This  should  be  done  in  the  open 
air;  no  blast  should  be  applied  to  the  fire.  After  the  chain 
has  been  heated  cherry  red,  it  should  be  placed  in  an  iron 
vessel,  the  bottom  of  which  has  been  covered  with' powdered 
charcoal.  Then  cover  the  chain  with  the  same  substance, 
close  the  box,  and  allow  the  chain  to  remain  there  until 
cold.  It  may  then  be  rove  through  the  blocks  again,  and 
will  be  nearly  as  good  as  when  new. 


SPLICES. 

7.  Definitions. — Splicing  is  the  operation  of  so  join- 
ing two  pieces  of  rope  as  to  obtain  one  continuous  piece 
with  no  appreciable  increase  of  diameter  at  the  splice. 
There  are  several  kinds  of  splices,  but  the  principal  ones  are 
the  short  splice,  the  lo7ig  splice,  and  the  eye  splice. 

The  principle  of  all  splicing  consists  of  joining,  or  marry- 
ing, the  strands,  thinning  them  out  and  tapering  them  so 
that  the  diameter  at  the  splice  is  the  same  or  only  slightly 
greater  than  that  of  the  rope  itself.  In  the  long  splice,  no 
increase  in  diameter  is  allowed. 

8.  Materials  Used  for  Ropes. — Until  comparatively 
recent  years,  all  ropes  were  made  of  vegetable  fiber  teased 
out  and  spun  into  suitable  form  either  by  hand  or  machinery ; 
but  since  the  introduction  of  iron,  and  particularly  of  mild 
steel,  into  the  rope-manufacturing  industry,  steel  rope  is 
rapidly  superseding  all  other  kinds  of  rope  for  certain  classes 
of  work.  For  many  purposes,  however,  fiber  ropes  are  still 
used  and  can  never  be  replaced  by  steel  ones;  they  are  made, 


§24 


SHOP  HINTS. 


7 


for  the  most  part,  either  of  hemp,  manila,  or  coir  (cocoanut 
husk  fiber).  First,  the  fibers  are  spun  into  yarns,  then  the 
yarns  into  strands,  and,  finally,  the  strands  into  rope.  The 
methods  of  splicing  described  and  illustrated  here  apply  only 
to  these  fiber  ropes. 

9.  Splicing  Instruments. — The  only  instruments 
necessary  for  making  a splice  are  a marl  inspike  and  a 
knife.  The  former  is  made  of  either  iron  or  hard  wood,  is 
from  12  to  14  inches  long,  and  about  1 inch  in  diameter  at 
the  thick  end,  the  other  end  being  sharpened  to  a blunt 


Fig.  4. 


point  about  as  shown  in  Fig.  4;  it  is  always  operated  by  the 
right  hand,  while  the  left  encircles  the  rope.  After  pushing 
the  point  through  the  rope,  between  the  strands  that  are  to 
be  separated,  the  thick  end  is  placed  against  the  body  of  the 
operator;  then,  using  both  hands,  the  rope  is  untwisted  so 
as  to  rendor  the  work  of  opening  the  strands  compara- 
tively easy. 

1 O.  Making  a Short  Splice. — Unlay,  that  is,  split 
open,  the  strands  at  the  end  of  each  rope  for  a distance 
about  as  shown  in  Fig.  5;  this  distance  depends  entirely  on 


8 


SHOP  HINTS. 


§24 


the  diameter  of  the  rope,  but  as  the  proportion  will  be  the 
same  for  all  diameters,  the  illustration  serves  as  a general 
guide.  Be  sure  to  unlay  enough;  a few  inches  too  much 

is  better  than  too 
little,  as  the  ends 
have  to  be  cut  off 
anyway.  Then,  place 
the  two  ends  together 
as  shown  at  ( a ),  so 
that  each  strand  lies 
between  two  strands 
of  the  other  rope. 
Now,  hold  the 
strands  x , y9  z and 
the  rope  A in  the  left 
hand;  if  the  ropes  are 
too  large  to  hold  in 
this  manner,  fasten 
them  together  with 
twine;  then  take  one 
of  the  strands,  say  n,  and  pass  it  over  strand  y,  and  having 
made  an  opening,  either  with  the  thumb  or  with  a marlin- 
spike  in  the  manner  illustrated  in  Fig.  4,  push  the  strand  n 
through  x and  pull  it  taut ; this  operation  is  known  as  stick- 
ing. Proceed  similarly  with  strands  m and  o , passing  each 
over  the  immediately  adjoining  strand  and  under  the  next 
one.  Perform  precisely  the  same  operation  with  the  strands 
of  the  other  rope,  passing  each  strand  over  the  adjoining 
one  and  under  the  next,  thus  making  the  splice  appear 
as  at  ( b ).  Now,  in  order  to  insure  security  and  strength, 
this  work  must  be  repeated  by  passing  each  strand 
over  the  third  and  through  under  the  fourth ; then,  after 
subjecting  the  splice  to  a good  stout  pull,  cut  off  the  ends 
of  the  strands,  and  the  finished  splice  as  shown  at  ( c ) is 
obtained. 

In  slings  and  straps  used  for  heavy  work,  the  strands 
should  be  passed  twice  each  way,  and  one-half  of  each 
strand  should  be  whipped , or  bound,  with  twine  to  one-half 


X 


<C) 


Fig.  5. 


§24 


SHOP  HINTS. 


9 


of  the  rest,  thus  preventing  the  strands  from  creeping 
through  when  the  splice  is  taxed  to  the  full  capacity  of 
the  rope. 

1 1.  Making  a Long;  Splice. — In  the  short  splice,  the 
diameter  at  the  joint  is  rather  greater  than  that  of  the  rope, 
for  which  reason  it  is  not  a suitable  .splice  where  the  rope  is 
to  be  used  in  tackles  and  pulley  blocks,  or  in  places  that  will 
not  admit  anything  larger  than  the  rope  itself.  In  such 
cases  the  long  splice  is  used.  When  properly  made,  the 
untrained  eye  can  hardly  distinguish  it  from  the  rest  of  the 
rope.  To  make  the  long  splice:  Unlay  the  ends  as  before, 
but  about  three  times  as  far,  and  place  them  together  as 


shown  at  Fig.  6 (a),  in  the  same  manner  as  for  the  short 
splice.  Then  unlay  one  of  the  strands  of  the  right-hand 
rope,  say  ;r,  and  in  the  groove  thus  made  lay  the  strand  of 
the  left-hancUrope,  taking  good  care  to  give  the  strand  the 
proper  twist,  so  bhat  it  falls  gracefully  into  the  groove  pre- 
viously occupied '-by  the  strand  x.  Do  likewise  with  the 
strands  y and  ;//,  unlaying  y gradually  and  in  its  place  laying 
the  strand  m\  the  result  is  shown  at  (/?).  Now,  leaving  the 
middle  strands  p and  g in  their  original  positions,  cut  off  all 
C.  S.  III.— 24 


10 


SHOP  HINTS. 


§24 


the  strands,  as  shown  at  ( b ) ; then  relieve  strands  n and  ;tr  of 
about  one-third  their  yarns,  and  with  what  is  left  cast  an 
overhand  knot,  exactly  as  shown;  no  other  kind  of  knot  will 
do.  Pull  this  knot  taut  and  dispose  of  the  ends,  as  in  the 
short  splice,  by  passing  them  over  the  adjoining  strand  and 
through  under  the  next,  cutting  off  a few  yarns  at  each 
stick.  Proceed  similarly  with  strands  p and  g,  and  y and  ///. 
The  splice,  when  it  is  completed,  appears  as  at  (c).  Some- 
times the  overhand  knot  is  made  without  first  thinning  the 
strands,  and  then  split  and  the  half  strand  put  through  as 
described,  but  by  doing  so  the  surface  of  the  splice  is  never 
as  smooth  as  by  the  other  method,  which,  for  strength  and 
neatness,  is  second  to  none. 

I 2.  Making  an  Eye  Splice. — Another  splice,  and 
one  that  is  as  common  and  useful  as  the  two  already 


described,  is  the  eye  splice  illustrated  in  Fig.  7.  To  begin 
this,  unlay  the  end  of  the  rope  about  as  far  as  for  the  short 
splice,  and  bend  into  the  required  size  of  eye,  as  shown 
at  (a).  Then  tuck  the  end- of  the  middle-strand  y under 
one  of  the  strands  of  the  standing  part,  having  previously 
made  the  necessary  opening  with  the  marlinspike,  and  pull 
tight,  getting  what  is  shown  at  (/?).  Now  push  the  strands 
from  behind,  and  under  the  strand  on  the  standing  part  next 


§24 


SHOP  HINTS. 


11 


above  that  under  which  the  middle  strand  y was  passed,  so 
that  it  will  come  out  where  y went  in,  getting  what  is  shown 
at  (r) ; then  pass  the  third  strand  z under  the  remaining  free 
strand  in  the  standing  part,  next  to  the  one  under  which  y 
was  passed,  getting  ( d ).  Now  pull  the  strands  taut,  and 
from  each  cut  out  one-third  of  the  yarns,  and  tuck  each  one 
under  its  corresponding  strand  twice  more;  give  it  a good 
stretching,  cut  off  the  ends,  and  thus  complete  the  splice, 
as  shown  at  (e). 


KNOTS,  BENDS,  AND  HITCHES. 

13.  In  Fig.  8 are  illustrated  a few  methods  of  making 
knots  and  bends,  applying  slings  and  ropes  to  hooks,  bar- 
rels, etc.,  and  a few  other  wrinkles  useful  to  those  engaged 
in  workshops.  Should  a rope  be  too  long  for  some  tempo- 
rary purpose,  do  not  cut  it,  but  arrange  it  as  at  (a);  if  sev- 
eral bights  are  laid  up  to  shorten  the  rope  to  the  required 
length,  pass  the  standing' part  through  and  over  the  ends  of 
all,  and  pull  tight.  At  (c)  is  shown  how  a sling  or  strap 
should  be  applied  to  a hook  when  the  rope  spreads  away  to 
its  load;  this  hitch  will  prevent  the  sling  from  slipping  in 
the  hook,  in  case  the  load  should  come  in  contact  with  some 
obstruction  while  being  hoisted.  At  ( b ) and  ( d ) is  shown 
how  a smaller  rope  should  be  secured  to  one  of  greater  diam- 
eter. The  Blackwall  hitch  is  illustrated  at  (e) ; except 
for  very  light  loads,  this  should  be  made  with  the  end  twice 
around  the  hook  (called  a double  hitch),  as  in  the  figure. 
Experience  has  proved  that  this  is  the  safest  way,  since  with 
only  one  turn,  the  end  is  liable  to  creep  when  subjected  to  a 
heavy  pull,  especially  in  damp  weather,  when  the  moisture 
absorbed  by  the  rope  acts  as  a lubricant.  When  a rope  is 
too  long  to  conveniently  secure  its  end  to  a tackle,  a bight 
of  it  twisted  as  at  (f)  is  very  handy  and  useful.  To  make 
this  hitch,  commonly  called  a cat’s  paw,  take  hold  of  the 
rope  with  both  hands  at  places  about  2 feet  apart,  and  twist 
it  two  or  three  times  each  way;  then  apply  the  ends  of  the 
loops  thus  made  to  the  hook.  The  twisting  prevents  the 


12 


SHOP  HINTS. 


§24 


rope  from  becoming  jammed,  and  the  hitch  is  very  easily 
undone.  At  (g)  is  shown  a timber  hitch,  so  simple  that 


explanations  are  unnecessary.  At  (//)  is  shown  how  to  apply 
a rope  to  a barrel  or  similar  vessel  when,  for  some  reason,  it 


§24 


SHOP  HINTS. 


13 


is  desired  to  hoist  it  in  a vertical  position.  At  (k)  is  shown 
what  is  known  as  a parbuckle  ; this  hitch  is  used  for  rais- 
ing a heavy  cask  or  similar  load  with  a single  length  of  rope. 

A very  useful  knot  that  should  be  mastered  by  every 
mechanic,  anti  by  all  persons  in  any  way  connected  with 
shipping,  is  shown  at  (/);  by  seamen,  this  is  known  as  the 
bowline  knot.  To  make  it,  take  the  end  of  the  rope  in 
the  right  hand  and  the  standing  part  in  the  left;  lay  the  end 
over  the  standing  part,  then,  with  the  left  hand,  turn  over 
the  end  a bight  (a  loop,  or  turn)  in  the  standing  part,  pass 
the  end  over  and  around  the  standing  part,  and  through  the 
bight  again,  thus  completing  the  knot;  all  this  is  shown  with 
perfect  clearness  in  the  illustration.  Probably  the  most 
common  knot  used  for  tying  two  ropes  together  is  the  square 
knot  shown  at  (in).  This  should  always  be  made  in  the 
manner  shown,  and  never  as  shown  at  (//),  which  is  some- 
times called  a granny's  knot. 


ERKCTION  OF  A DERRICK. 

14.  Description  of  tbe  Derrick. — A common  form 
of  derrick  is  shown  in  Fig.  9.  It  consists  of  a mast  a , the 
lower  end  of  which  is  set  into  a base  b that  is  secured  to  the 
timber  framing  c shown  in  the  illustration.  The  upper  end 
of  the  mast  carries  the  so-called  derrick  head d , to  which  the 
guy  ropes  e , g,  and  h are  fastened.  These  guy  ropes  are 
fastened  to  stakes  driven  into  the  ground,  or  to  any  other 
immovable  objects  that  are  conveniently  located,  and  serve 
to  steady  the  mast.  The  mast  has  pivots  at  both  ends  that 
enter  sockets  in  the  base  and  in  the  derrick  head,  and  allow 
the  mast  to  be  rotated.  The  boom  i is  pivoted  to  the  mast 
at  k,  and  can  be  raised  or  lowered  by  the  tackle  l.  The 
tackle  m is  used  for  hoisting  weights. 

When  the  masjt  alone  is  used  in  hoisting,  i.  e.,  when  no 
boom  is  furnished,  the  mast  is  called  a *>in  pole.  When 
the  upper  end  of  the  mast  and  boom  are  tied  together 
by  a horizontal  member,  the  whole  device  is  called  a crane, 


14  SHOP  HINTS.  §24 

and  is  usually  fitted  with  a traveling  carriage  on  the 
horizontal  part,  or  gib. 


15.  Erecting  the  Gin  Pole. — When  it  is  desired  to 
erect  a tall  derrick,  it  will  generally  be  necessary  to  put  up 
a gin  pole  first  to  assist  in  raising  the  mast,  but  if  the  der- 
rick is  low,  its  boom  may  be  used  for  this  purpose.  One 
method  of  erecting  the  gin  pole  is  to  slip  a bar  of  iron  a 
through  the  hole  in  the  lower  end  and  secure  it  to  suitable 
stakes  c,  as  shown  in  Fig.  10.  The  free  end  of  the  gin  pole 
is  then  lifted  from  the  ground  and  placed  on  the  X-shaped 
brace  e.  The  guys  f,  g,  h , and  i are  then  attached  to  the 


24 


SHOP  HINTS. 


15 


upper  end  d and  are  laid  out  on  the  ground  ready  for  use. 
The  men  now  raise  the  gin  pole  b by  means  of  pike  poles 
and  advance  the  support  e toward  the  lower  end.  When 
the  free  end  has  been  raised  some  distance  from  the  ground, 
the  ropes  f and  i may  be  pulled,  and  thus  help  to  raise  the 


fig.  10. 


gin  pole  to  a vertical  position;  at  the  same  time,  the  men 
who  attend  to  the  guys  g and  h must  see  that  it  does  not 
shift  from  the  desired  position.  Usually  only  one  man  is 
required  for  each  end  of  the  guys  g and  Ji,  since  he  can  wind 
the  rope  about  a stake,  and  then  easily  prevent  the  gin  pole 
from  moving  too  far. 

16.  Erecting  the  Mast. — After  the  gin  pole  has  been 
raised  into  an  upright  position  and  the  guys  have  been  fast- 
ened, it  may  be  used  for  lifting  the  mast,  as  is  shown  in 
Fig.  11,  in  which  a represents  the  gin  pole,  the  lower  end 
of  which  is' lashed  to  the  stakes  c.  The  base  for  the  der- 
rick having  been  located  and  fastened  to  the  timbers  b , b , 
the  mast  <3^4s  hoisted  into  position  by  means  of  a rope 
fastened  a little  above  its  center  and  passed  over  the  pulley  e 
on  the  end  of  the  gin  pole.  The  other  end  of  this  rope  f 
may  be  handled  by  hand  if  the  mast  is  not  too  heavy,  or  by 
a suitably  located  winch  or  crab  if  the  mast  is  of  consid- 
erable weight.  The  derrick  head  g should  be  placed  in 


16 


SHOP  HINTS. 


§24 


position  and  the  guys  attached  before  the  mast  is  raised. 
The  lower  end  of  the  mast  is  now  lowered  into  the  base, 


Fig.  11. 


after  which  the  guys  attached  to  the  head  g are  tightened 
and  fastened  in  position.  The  temporary  guys  /i,  i,j \ and  k 


SHOP  HINTS. 


1? 


§ 24 

for  the  gin  pole  are  usually  of  manila  or  hemp  rope,  while 
the  permanent  guys  for  the  mast  are  made  of  wire  rope. 

1 7.  Placing  the  Boom. — After  the  mast  has  been 
properly  guyed  and  the  gin  pole  has  been  taken  down,  a 
hoisting  rope  is  passed  over  the  pulleys  at  the  top  of  the 
mast;  a hitch  is  then  made  around  the  boom  and  it  is  raised 
until  the  bottom  end  can  be  swung  into  the  knee,  where  it 
is  secured  by  its  pin.  The  ropes  are  then  all  reeved  through 
their  proper  pulleys  and  the  derrick  is  ready  for  work. 

Large  derricks  are  generally  erected  by  the  aid  of  a sepa- 
rate gin  pole,  as  just  described.  In  the  case  of  a very  large 
derrick  it  is  sometimes  necessary  to  erect  a gin  pole  of  a 
height  such  that  the  men  can  handle  it,  and  use  this  for  set- 
ting the  boom  on  end,  which  is  then  used  as  a gin  pole  for 
lifting  the  mast.  In  some  cases  two  separate  sticks  of  timber 
are  used  as  gin  poles,  a short  one,  less  than  one-half  the 
height  of  the  mast,  being  used  to  set  a gin  pole  about  two- 
thirds  the  height  of  the  mast;  this  second  gin  pole  is  then 
employed  for  setting  both  the  mast  and  the  boom.  Derricks 
so  large  as  to  require  two  gin  poles  for  their  erection  are 
rarely  used  except  on  permanent  work. 

18.  Erecting  a Small  Derrick. — With  small  der- 
ricks, it  is  rarely  necessary  to  use  a gin  pole  for  raising  the 
mast,  as  the  boom  is  generally  light  enough  to  be  erected 
as  a gin  pole,  and  is  then  used  for  raising  the  mast.  After 
the  mast  has  been  raised  and  securely  guyed,  the  mast  itself 
is  used  for  swinging  the  boom,  which  up  to  this  time  has 
served  as  a gin  pole,  into  position. 

19.  Dismantling  tlie  Derrick. — When  the  work  has 
been  finished  and  it  becomes  necessary  to  dismantle  the  der- 
rick, the  boom  is  hoisted  up  to  the  mast,  and  is  detached 
from  the  knee.  Stakes  are  then  driven  into  the  ground  and 
the  lower  end  of  (the  boom  is  lashed  to  them;  the  boom  is 
then  used  as  a gin  pole  for  lowering  the  mast.  The  boom 
itself  is  lowered  afterwards  by  paying  out  two  of  its  tempo- 
rary guys  until  it  can  be  caught  on  a support  similar  to  that 
shown  at  e}  Fig.  10. 


18 


SHOP  HINTS. 


24 


MISCELLANEOUS  OPERATIONS. 


CLEANING  WORK  ANI)  CASTINGS. 


THE  SODA  KETTLE. 

20.  Description  of  tlie  Kettle.  — All  shops  have  x 
more  or  less  work  that  must  be  cleaned  so  as  to  be  free 
from  grease.  This  is  often  a troublesome  task,  involving 
the  expenditure  of  time  and  energy.  The  greater  the 
irregularity  of  the  pieces,  the  more  trouble  there  is  experi- 
enced in  cleaning  them. 

A very  convenient  method  of  quickly  and  easily  cleaning 
small  parts  of  machines,  tools,  or  machined  parts  is  to  wash 

them  in  hot  soda  water. 
The  most  convenient 
receptacle  for  this  mix- 
ture is  known  in  the 
shop  as  a soda  kettle. 
This  is  often  a shop- 
made  affair,  but  e m - 
bodies  the  main  features 
of  the  kettle  illustrated 
in  Fig.  12.  This  soda 
kettle,  which  is  built  by 
a well-known  tool 
builder,  consists  of  a 
cast-iron  kettle  a con- 
taining a coil  of  steam 
pipe  for  heating  the 
soda  water.  Live  steam 
enters  the  coil  when  the  globe  valve  b is  opened,  and  the 
exhaust  steam  leaves  through  the  pipe  c , which  is  provided 
with  a globe  valve.  A by-pass  pipe  d having  a globe  valve 
is  connected  to  the  exhaust  pipe;  if  the  globe  valve  in  the 
exhaust  pipe  is  closed  and  the  valve  in  the  by-pass  pipe  is 
opened,  the  pressure  of  the  live  steam  will  force  the  water 


24 


SHOP  HINTS. 


19 


of  condensation  in  the  bottom  of  the  coil  into  the  kettle. 
A drain  cock  e is  used  for  emptying  the  kettle. 

21.  Operation  of  the  Kettle. — In  use,  the  kettle  is 
filled  about  three-fourths  full  of  clean  water  to  which  is 
added  about  its  volume  of  sal  soda;  the  mixture  is  then 
heated  as  hot  as  the  steam  will  heat  it.  A wire  basket,  or  an 
iron  pail  or  bucket  having  the  bottom  punched  full  of  holes, 
is  provided  for  holding  small  pieces  while  dipping  them 
into  the  soda  mixture.  Suitable  hooks  made  of  small  iron 
rod  may  be  used  to  dip  single  pieces  into  the  kettle.  A 
pair  of  pick-up  tongs  and  one  or  two  hooks  should  be  kept 
near  the  kettle,  since  pieces  are  sometimes  dropped  into  it 
and  must  be  fished  out.  Work  covered  with  soft  grease  or 
oil  and  chips  is  cleaned  by  putting  it  into  the  basket,  which 
is  then  dipped  into  the  hot  water.  Work  that  may  be 
covered  with  oil  that  has  dried  on  it  often  has  to  be  soaked 
in  the  solution  for  some  time,  and  a part  of  the  dried  oil 
then  has  to  be  scraped  off  ; the  work  is  now  given  a further 
soaking,  which  is  generally  sufficient  to  remove  the  rest  of 
the  dried  oil.  Work  cleaned  in  the  hot  soda  water  dries 
quickly  and  will  not  rust. 


PICKLING  SOLUTIONS. 

22.  Sulpll  uric  Acid  for  Pickling.  — The  surfaces 
of  castings,  drop  forgings,  and  many  of  the  materials  used 
in  the  construction  of  machinery  require  cleaning  or  prep- 
aration before  they  can  be  used.  Much  of  this  cleaning 
is  done  by  pickling  the  work  in  such  mixtures  as,  by  experi- 
ment, have  been  found  to  be  most  effective.  Several  of 
these  solutions  are  given  below,  and  the  user  can,  by  experi- 
ment, determine  which  of  these  is  best  adapted  to  his  needs. 

Oil  of  vitriol,  oi^sulphuric  acid,  is  one  of  the  most  common 
acids  used  for  pickling.  It  is  generally  transported  in  glass 
carboys,  which  are  securely  boxed  up.  The  acid  is  handled 
in  small  quantities  around  the  works  in  glass,  earthen,  or 
lead  vessels  It  is  used  in  the  proportion  of  about  1 part 
of  acid  to  4 parts  of  water,  for  cleaning  sand  and  scale  from 


20 


SHOP  HINTS. 


§24 


iron  castings,  although  some  use  a larger  proportion  of 
water.  Pure  sulphuric  acid  will  not  attack  iron,  but  the 
dilute  acid,  or  the  acid  mixed  with  water,  will  do  so. 

23.  The  Pickle  Bed. — The  cleaning  is  generally  done 
in  what  is  called  a pickle  bed,  which  consists  of  a lead- 
lined  trough  for  holding  the  solution.  At  one  side  of  it  is 
a sloping  wooden  platform,  so  that  the  solution  will  flow 
from  it  to  the  trough.  The  castings  are  piled  upon  this 
platform  and  the  solution  is  poured,  over  them  with  a ladle. 
They  are  allowed  to  lay  over  night  ; it  will  then  be  found 
that  the  acid  has  attacked  the  surface  of  the  iron  suffi- 
ciently to  loosen  the  sand,  much  of  which  is  washed  away 
with  water.  The  castings  are  further  cleaned  with  wire 
brushes  and  old  files. 

24.  Hydrofluoric  Acid  as  a Pickling  Mixture. 

Wrought  iron  that  is  badly  scaled  in  forging  may  be  cleaned 
with  a solution  of  1 part  of  sulphuric  acid  to  10  parts  of 
water  ; after  pickling,  the  work  should  be  cleaned  in  hot 
lime  water.  Another,  and  in  many  respects,  better,  solution 
is  composed  of  1 part  of  hydrofluoric  acid  to  10  parts  of 
water.  This  is  kept  in  a wooden  vat  ; the  castings  are 
immersed  in  it  for  2 or  3 hours.  Hydrofluoric  acid  does 
not,  like  sulphuric  acid,  attack  iron,  but,  instead,  attac'ks 
the  sand  directly  and  eats  it,  as  well  as  the  hard  magnetic 
oxide  (the  scale).  About  half  as  much  hydrofluoric  acid  is 
used  as  would  be  needed  of  the  sulphuric  acid,  and  the 
work  is  done  in  about  one-fourth  the  time.  The  pickling 
vat  may  be  filled  and  used  two  or  three  times  before  adding 
more  acid.  Drop  forgings  are  often  covered  with  a thick, 
hard  scale  that  may  be  removed  by  dipping  them  in  this 
mixture,  then  washing  them  in  clear  water.  Care  should 
be  taken  to  keep  this  acid  from  the  hands,  as  it  burns 
severely  in  a few  hours.  If  it  is  spilled  upon  the  hands, 
they  should  be  washed  in  water  mixed  with  aqua  ammonia, 
or  some  other  alkali,  in  order  to  prevent  injury. 

Brass  castings  are  pickled  in  a mixture  of  1 part  of  nitric 
acid  to  5 parts  of  water  and  washed  thoroughly  after  pickling. 


§24 


SHOP  HINTS. 


21 


COMPRESSED  All?  FOR  CLEANING. 

25.  In  shops  having  compressed-air  service,  a |~inch 
rubber  hose  with  a -|-inch  nozzle  attached  to  it  forms  a con- 
venient means  of  cleaning  many  pieces  of  work  that  are  so 
shaped  that  it  is  difficult  to  reach  every  part  with  the  hand. 
The  blast  is  simply  turned  on  the  piece  to  be  cleaned,  and 
most,  if  not  all,  of  the  loose  dirt  is  blown  off.  An  air  hose 
will  be  found  very  useful  in  the  tool  room  for  cleaning  the 
shelves,  racks,  and  drawers,  and  may  even  be  used  advan- 
tageously for  rapid  cleaning  of  some  tools.  The  disadvan- 
tage of  the  air  blast  lies  in  the  fact  that  it  scatters  the  dirt 
all  over  the  vicinity. 

PROTECTIVE  COVERINGS  FOR  METALS. 


GALVANIZING. 

26.  Preparing  tlie  Iron  for  Galvanizing. — Gal- 
vanizing iron  consists  in  providing  it  with  a tightly  adher- 
ing coating  of  zinc.  This  makes  it  practically  waterproof, 
and  it  is  of  good  advantage  even  if  afterwards  coated  with 
protective  paint.  All  castings  that  are  continually  exposed  to 
the  weather  should  be  galvanized,  unless  otherwise  protected. 

The  process  consists  in  the  preparation  of  the  casting  or 
other  articles  to  receive  the  coating,  and  the  actual  immer- 
sion in  the  bath  of  melted  zinc.  The  castings  are  first  freed 
from  as  much  sand  as  possible  in  the  foundry.  Malleable 
castings  are  usually  clean  enough  for  this  purpose  when  they 
leave  the  soft-casting  cleaning  room.  Next,  they  are  placed 
in  large  vats  containing  dilute  sulphuric  or  hydrofluoric 
acid,  the  latter  being  used  only  in  obstinate  cases,  as  a rule. 
Here  they  remain  until  the  coating  of  oxide  is  thoroughly 
removed.  Ror  large  work,  the  vats  are  sometimes  30  feet 
long,  6 feet  wide,  and  4 feet  deep,  and  have  steam  pipes 
to  warm  the  solution  in  cold  weather,  though  usually 
the  chemical  reactions  warm  the  pickle  sufficiently.  The 
castings  may  remain  in  the  pickle  over  night,  being  stirred 
frequently  so  that  pockets  of  gas  that  have  formed  may  not 


22 


SHOP  HINTS. 


24 


cover  a spot  and  prevent  the  acid  from  touching  it,  as  these 
spots  would  not  galvanize  properly.  Castings  are  also  repeat- 
edly taken  out  and  scratched  with  a chisel  or  old  file  to  note 
how  the  action  of  the  acid  progresses.  When  the  process  is 
finished,  the  acid  maybe  drawn  off  into  another  tank,  prefer- 
ably by  means  of  a steam  siphon,  or  it  may,  as  is  usually  the 
case,  be  left  in  the  tank,  and  the  castings  transferred  into 
a second  tank  containing  clean,  warm  water.  Small  castings 
are  always  wired  together  or  put  into  perforated  wooden 
boxes  so  that  they  cannot  be  lost.  In  this  second  tank  the 
acid  is  washed  off,  and  the  pieces  should  be  thoroughly 


examined.  The  work  could  now  go  to  the  drying  oven  and 
then  into  the  zinc  pots,  but  an  improved  method  introduces 
another  pickling  in  dilute  hydrochloric  acid,  in  which  the 
work  remains  long  enough  to  be  again  attacked  thoroughly. 
When  lifted  from  this  solution  the  castings  are  placed  in  a 
large  drying  oven,  shown  in  Fig.  13,  to  be  dried  and  heated 
preparatory  to  the  galvanizing  process.  These  drying  and 
heating  ovens  are  usually  constructed  of  brick  and  have 
doors,  as  shown  at  a,  a , of  sheet  iron  on  each  end,  each  door 
being  the  full  width  of  the  oven.  This  facilitates  the  placing 
and  removing  of  the  material  and  enables  the  operation  to  be 
performed  so  quickly  that  little  heat  is  lost.  The  fire  is 


§24 


SHOP  HINTS. 


23 


built  on  the  grate  at  b,  from  which  the  gases  with  the  heat 
pass  through  the  chamber  c , heating  the  oven  from  below, 
and  into  the  oven  through  the  opening  d , and  finally  out 
again  through  e. 

27.  Coating  the  Work  With  Zinc. — It  seems  that 
the  second  pickling  in  hydrochloric  acid  impregnates  the  sur- 
face of  the  iron  with  a chloride  of  iron,  which,  on  being  dried, 
protects  the  iron  surface  from  rusting.  Again,  the  dried 
chloride  of  iron,  on  touching  the  melted  zinc,  is  volatilized, 
leaving  a clean  surface  of  pure  iron  behind,  and  this  surface 
in  a rough  state  increases  the  tendency  of  alloying  with 
zinc.  The  consequence  is  that  no  difficulty  is  experienced  in 


fig.  14. 


getting  the  zinc  to  adhere;  hence,  when  the  castings  come 
from  the  heating  oven,  they  go  directly  into  the  bath  of 
melted  zinc.  This  bath  is  practically  a tank  furnace,  one 
form  of  which  is  shown  in  Fig.  14  (a)  and  ( b ).  A tank  of 
suitable  size,  according  to  the  character  of  the  work  treated, 
is  made  of  heavy  steel  plates  riveted  to  an  angle-iron  frame, 
as  shown  at  b , Fig.  14  (a). 

This  tank  is  bricked  into  a furnace  arranged  with  fire-pots 
at  regular  intervals,  as  shown  at  c , c,  which  are  required  to 
keep  the  zinc  at  the  proper  temperature.  Air  drafts,  as 
shown  at  d , are  provided  for  each  fire-pot. 

It  is  important  that  the  castings  coming  from  the  drying 
oven  lose  no  %at,  for  such  a loss  has  the  effect  of  chilling 
the  bath,  which  means  delay  in  getting  out  the  work.  Small 
castings  are  also  kept  wired  together  in  the  zinc  bath.  When 
taken  out,  the  surplus  zinc  is  shaken  off  and  the  castings 
are  sometimes  quenched  in  cold  water,  although  this  may 
injure  the  castings,  sometimes  cracking  or  breaking  them. 
Large  castings  are  handled  with  a tackle  suspended  above 


24 


SHOP  HINTS. 


§24 


the  tank,  while  the  surplus  zinc  is  taken  off  with  a trowel 
and  wet  broom.  . Small  castings,  if  it  is  impossible  or  unde- 
sirable to  wire  them  together,  are  placed  in  large  dippers 
made  of  coarse  wire-screen  material,  and  all  dipped  into  the 
molten  zinc.  Some  galvanizing  works  do  not  use  drying 
and  heating  ovens,  but  take  their  castings  in  small  quanti- 
ties directly  from  the  acid  bath  to  the  zinc  bath,  and  let  this 
heat  them.  This  practice -is  not  a very  good  one,  as  it  dete- 
riorates the  zinc  in  the  bath  and  leaves  a bad  looking  sur- 
face on  the  casting.  After  the  castings  are.galvanized  they 
are  sometimes  carried  through  the  quenching  water  on  a 
chain  carrier,  and  at  this  point  the  inspection  should  be 
made  and  faulty  work  returned  to  the  tanks  for  regalvani- 
zing. During  the  galvanizing  process,  dry  sal  ammoniac  is 
thrown  on  the  work  as  it  is  dipped  in  and  out  of  the  bath  of 
zinc,  to  help  the  alloying  process.  Dense  fumes  of  sal 
ammoniac  fill  the  room,  but  they  are  not  seriously  dangerous 
to  health.  It  is  well  to  have  some  grease  on  the  zinc  bath, 
as  this  keeps  the  zinc  from  oxidizing  rapidly  and  also  assists 
in  the  alloying  of  the  zinc  with  the  iron  surface  to  be  coated. 
The  castings  finally  go  to  the  warehouse  for  shipment. 

28.  Recovering  tlie  Waste  Zinc. — The  oxidation 
of  the  zinc  is  one  of  the  most  serious  things  with  which  the 
galvanizer  has  to  contend,  as  it  gradually  renders  the  zinc 
unfit  for  use.  A certain  amount  of  iron  is  removed  from 
the  castings  and  from  the  tank.  This  iron  enters  the  zinc 
bath,  and,  uniting  with  the  zinc,  forms  an  alloy  called  dross, 
which  settles  to  the  bottom  of  the  tank,  and  if  left  there  will 
soon  form  a hard  cake  and  ruin  the  tank.  The  continuous 
application  of  excessive  heat  will  result  in  the  blistering  and 
burning  out  of  the  steel  plates.  Once  or  twice  a week,  there- 
fore, a large  iron  scoop,  shaped  like  a large  snow  shovel,  and 
operated  from  above  by  the  tackle,  is  pushed  down  into  the 
tank,  and  the  dross  lifted  out.  Perforations  in  the  scoop 
allow  the  good  zinc  to  drain  off,  and  the  dross  is  poured 
into  iron  molds,  where  it  quickly  solidifies.  It  is  then 
dumped  and  piled  for  sale  to  the  zinc-refining  companies. 
When  it  is  understood  that  sometimes  one-fourth  of  the 


SHOP  HINTS. 


25 


§24 

whole  bath-is  dross  at  the  end  of  a week  of  continuous  gal- 
vanizing-, and  that  the  dross  is  90  per  cent,  zinc,  the  serious- 
ness of  the  loss  becomes  apparent.  The  dross  can  be 
refined  again  by  melting  with  lead  and  rabbling  with  green 
poles,  but  it  hardly  pays  galvanizers  to  attempt  this,  as  the 
zinc-refining  companies  have  special  facilities  for  the  pur- 
pose and  do  the  work  at  moderate  cost. 

The  skimmings  of  the  zinc  bath  and  floor  sweepings  should 
also  be  preserved,  as  they  contain  considerable  zinc.  Much 
of  the  zinc  is  recovered 
from  them  by  treating  the 
material  in  a special  roast- 
ing furnace,  as  shown  in 
Fig.  15,  with  an  inclined 
hearth,  shown  at  a.  Small 
quantities  are  treated  at  a 
time,  the  particles  of  scat- 
tered zinc  collecting  as 
they  run  down  in  the  little 
well  shown  at  b , at  the 
bottom  of  the  pan,  from 
whence  the  zinc  is  tapped 
through  the  opening 
shown  at  c into  the  vessel 
shown  at  d.  What  re- 
mains of  the  roasted  ma- 
terial is  barreled  and  sold. 

The  furnace  here  illus- 
trated has  a firing  door 
an  ash  door  grates  g , 
a flue  y^a  hood  i,  and  an 
opening  froitp  the  hood  j,  through  which  the  fumes  from 
the  zinc  pass.  This  process  is  very  trying  to  the  immediate 
neighborhood  on  account  of  the  fat  used  to  cover  the  bath 
of  the  zinc,  much  of  which  finds  its  way  into  the  skim- 
mings and  results  in  very  bad-smelling  fumes.  The  roast- 
ing should  therefore  be  done  only  at  night,  unless  some 
provision  is  made  for  the  disposal  of  the  fumes. 

C.  S.  III.— 25 


26 


SHOP  HINTS. 


§24 


29.  Some  Precautions  and  Suggestions  in  Gal- 
vanizing.— With  hollow  castings,  pipe,  etc.,  great  precau- 
tion must  be  taken  to  keep  out  of  the  way,  for  if  any  moisture 
has  remained  in  the  pipe  and  comes  in  contact  with  the  hot 
zinc,  it  will  cause  an  explosion,  throwing  quantities  of  the 
melted  zinc  from  the  end  of  the  casting  with  great  force. 

The  same  holds  true  in  quenching  a pipe  in  cold  water, 
although  here  the  projected  water  is  not  so  serious.  Glycer- 
ine is  often  used  to  add  to  the  .grease  on  the  melted  zinc,  as 
it  is  said  to  give  fine  results  when  good  color  and  crystalliza- 
tion on  the  surface  are  wanted. 

A good  way  to  prevent  the  dross  from  adhering  to  the 
bottom  of  the  tank,  as  well  as  to  facilitate  its  removal,  is  to 
introduce  a quantity  of  lead  into  the  zinc  bath.  Lead  does 
not  alloy  with  either  zinc  or  iron;  it  has  a greater  density 
than  either,  and,  therefore,  sinks  to  the  bottom,  forming  a 
liquid  cushion  on  which  the  dross  and  other  impurities  float. 


TIXMXG. 


30.  Tinning  by  Dipping  the  Work  Into  Molten 
Tin. — Tinning  castings  differs  from  galvanizing  only  in  the 

substitution  of  tin  for  zinc 
and  in  general  carrying  on 
the  process  on  a much 
smaller  scale.  The  work 
when  small  is  all  put  into 
wire  baskets  and  pickled, 
after  which  the  basket 
with  the  well-pickled  cast- 
ings is  slowly  lowered  into 
the  bath  of  tin.  This  is 
usually  done  with  a small 
tackle,  and  when  thor- 
oughly tinned  the  basket 
is  raisedandthetin  allowed 
FlG'  16'  to  drip  off.  The  castings 

are  then  dumped  into  a wooden  chute,  shown  in  Fig.  16, 


[ 

^ J 

1 

!, 

§24 


SHOP  HINTS. 


27 


which  has  inclined  wooden  shelves,  as  shown  at  a,  which 
throw  the  castings  violently  against  each  other  as  they 
descend.  The  consequence  is  that  the  remaining  surplus 
tin  is  jarred  off,  the  pieces 
cool  without  remaining  in 
contact  with  each  other, 
and  are  quenched  practi- 
cally singly  as  they  fall 
into  the  water  shown  at  b. 

They  are  finally  rolled  in 
sawdust  in  order  to  dry 
them  thoroughly,  and  are 
then  packed  for  shipment. 

The  tinning  furnace  ordi- 
narily used  resembles  a 
crucible  furnace,  and  is 
illustrated  in  Fig.  17.  A 
firebox  is  shown  at  a , with 
its  ash-pit  at  b and  flue  for 
escaping  gases  at  c.  The 
iron  kettle  shown  at  c/isin 
direct  contact  with  the 
flame,  thus  heating  readily.  Above  the  kettle  is  the  hood 
shown  at  e for  collecting  the  fumes  and  directing  them 
toward  the  opening,  shown  at  /,  into  the  chimney. 


31.  Tinning  by  tlie  Cold  Process. — When  block  tin 
is  dissolved  in  hydrochloric  acid  and  a little  mercury,  an 
alloy  is  formed  that  can  be  readily  used  in  tinning  articles 
without  heating  either  the  tin  or  the  work.  Some  make  the 
alloy  of  1 part  of  tin,  6 of  mercury,  and  2 of  zinc,  by  weight. 
The  tin  and  mercury  are  mixed  together  until  a soft  paste 
is  formed.  The  articles  to  be  tinned  should  be  cleaned  by 
some  of  the  methods  previously  explained,  and  then  rubbed 
with  a rag  dampened  in  hydrochloric  acid.  The  alloy 
should  be  applied  to  the  surface  at  once  and  rubbed  with  the 
hydrochloric  acid.  By  this  method  it  is  very  easy  to  cover 
iron,  steel,  or  copper  with  a complete,  but  thin,  coating  of  tin. 


28 


SHOP  HINTS. 


24 


FILLING  AM)  FAINTING  MACHINE  TOOLS. 

32.  Most  machine  tools  are  finished  by  giving  them  a 
coat  of  paint.  The  surfaces  of  the  castings  are  cleaned  first 
in  the  foundry  scratch  room,  and  any  remaining  dirt  or 
irregularities  and  unevennesses  of  joined  parts  are  removed 
during  erection  by  chipping  and  filing  so  far  as  may  be 
necessary  to  make  a good  surface.  The  shop  painter  next 
goes  over  the  surfaces  with  a filler,  which  is  a kind  of  thick, 
heavy  paint,  very  adhesive  and  quick- drying.  It  is  applied 
with  a putty  knife,  as  it  is  about  as  thick  as  very  soft  putty 
or  freshly  opened  white  lead.  This  filler  hardens  rapidly 
when  exposed  to  the  air.  The  filled  surfaces  are  then 
smoothed  by  wetting  and  rubbing  them  with  a piece  of 
grindstone  or  a piece  of  a broken  emery  wheel,  or  by  simply 
rubbing  them  with  coarse  sandpaper.  When  the  smoothing 
has  been  finished,  one  or  two  coats  of  paint  having  the 
desired  color  are  applied.  Green  paint  is  preferred  by  some 
builders  and  shop  superintendents,  as  it  gives  a lighter 
appearance  to  the  shop  than  black  paint.  Green  and  even 
lighter  paints  are  much  used  for  machine  tools,  and  if  the 
painted  surfaces  are  covered  with  a varnish  that  will  resist 
oils,  they  are  easily  kept  clean  and  the  general  appearance 
of  the  shop  is  thus  much  improved.  Steel-gray  metallic 
paint  is  a favorite  paint  with  many  builders  on  account  of 
the  handsome  appearance  it  gives  to  the  machines. 


NOTES  ON  SHOP  ECONOMY. 


COST  OF  CONSTRUCTION. 

33.  Large  Quantities  Can  Be  Made  at  Low  Prices. 

The  question  of  cost  in  constructing  a machine  or  device  is 
one  of  great  importance  in  machine-shop  operations,  since 
the  question  of  whether  to  build  or  not  to  build  depends  on 
it.  It  is  an  every-day  occurrence  for  men  to  go  to  a machine 
shop  and  ask  to  have  a part  of  a tool  or  a machine  made,  and 
to  be  told  that  the  piece  would  cost  more  than  the  price  paid 


§24 


SHOP  HINTS. 


29 


for  the  whole  tool  or  machine  when  it  was  new.  The  reason 
for  the  low  cost  of  the  whole  machine  and  the  seeming  high 
price  for  the  single  piece  lies  in  the  fact  that  the  maker  of 
the  machine  or  device  had  special  tools  for  every  operation 
and  trained  help  to  do  the  work,  which  was  done  in  large 
lots,  perhaps  hundreds  at  a time,  and  could  thus  be  produced 
very  cheaply.  But  the  man  that  is  called  on  to  make  single 
parts,  one  at  a time,  either  has  to  use  such  tools  as  he 
happens  to  have,  or  has  to  make  special  ones  that  will  be  of 
no  use  on  any  other  work,  and  that  must  be  paid  for  by  the 
customer. 

The  cost  of  constructing  the  model  of  a typewriter, 
bicycle,  sewing  machine,  or  any  similar  piece  of  mechanism 
frequently  runs  up  into  thousands  of  dollars,  since  every 
part  is  made  by  hand ; but,  the  manufactured  article,  where 
every  part  is  made  in  large  quantities  on  the  interchange- 
able plan,  and  with  special  tools,  fixtures,  and  workers,  is 
built  for  a few  dollars. 

34.  Cost  of  Pattern  Work. — In  foundry  work  the 
same  condition  exists.  A customer  frequently  wants  some 
comparatively  simple  casting,  weighing  perhaps  only  a few 
pounds,  but  which  requires  the  making  of  a special  pattern. 
Evidently  the  cost  of  the  pattern  must  be  included  in  the 
price  charged  for  the  casting.  Then,  though  the  value  of 
the  iron  may  be  only  ten  cents  or  less,  it  may  cost  five  or 
ten  dollars  to  make  the  pattern  for  this  small  casting;  and 
this  must  be  paid  for  by  the  customer.  As  a matter  of 
course,  if  a large  number  of  castings  are  to  be  made  from 
one  pattern,  the  cost  of  the  pattern  is  distributed  among  so 
many  castings  that  the  cost  of  each  is  quite  low.  For 
instance,  it  costs  several  thousand  dollars  to  make  the  pattern 
for  a stove,  but  the  finished  stove  can  be  sold  at  a very  low 
price  on  account  of  the  large  number  of  castings  made  from 
each  pattern. 

35.  Cheapening  by  Duplication.  — If  only  one 
machine  or  engine  of  a kind  is  to  be  built,  the  work  must  be 
done  with  such  tools  as  are  at  hand  and  such  other  ordinary 


30 


SHOP  HINTS. 


§ 24 

tools  as  may  be  bought  or  made  on  the  premises;  but,  if  a 
large  number  of  the  same  kind  of  engine  or  machine  is  to 
be  built,  special  tools  can  be  provided  for  the  different  oper- 
ations and  the  same  operation  can  be  performed  on  all  the 
pieces  in  succession,  thus  saving  the  time  that  would  be 
required  for  changing  tools  and  machines  if  each  separate 
piece  were  finished  all  over  at  one  time.  It  should  be  kept 
in  mind  that  it  costs  just  about  as  much  to  rig  up  a machine 
or  get  it  ready  to  perform  an  operation  for  a single  piece  as 
it  does  to  do  the  same  thing  for  a dozen  ora  hundred  pieces; 
hence,  wherever  it  can  be  done,  the  whole  number  of  the 
same  operations  should  be  performed  before  making  a 
change.  This  statement  applies  to  all  parts  and  all  stages 
of  the  work,  from  starting  on  the  rough  forgings  and  cast- 
ings to  inspecting  and  painting. 


TIME  ELEMENT  IN  WORK. 

36.  Rate  of  Speed  in  Doing  Work.  — Any  one 

engaged  in  mechanical  work,  be  he  apprentice  or  journey- 
man, should  always  have  the  clock  in  mind.  This  state- 
ment does  not  refer  to  watching  the  clock  for  quitting  time, 
which  comes  quickly  enough  to  those  really  interested  in 
their  work,  but  to  the  time  element  in  connection  with  the 
work.  No  doubt  the  principal  object  is  to  do  the  work 
right,  but  between  two  men,  each  doing  it  equally  well,  the 
one  that  completes  the  work  in  the  shorter  time  is  the  better 
man,  the  one  who  should  and  generally  will  receive  the 
higher  wages,  and  the  one  who  is  less  liable  to  be  “ laid  off  ” 
when  business  is  dull.  It  is  well,  therefore,  for  a person  to 
cultivate  the  habit  of  working  as  rapidly  as  the  character  of 
the  work  will  permit,  first  making  up  his  mind  as  to  the  time 
a piece  of  work  should  take,  and  then  doing  his  best  to 
shorten  that  time.  Some  think  that  they  will  first  learn  to  do 
the  work  well  regardless  of  time,  and  afterwards  learn  to  do 
it  quickly;  but  this  plan  is  open  to  the  practical  objection 
that  having  once  learned  a rate  of  doing  work  it  is  hard  for 
us  to  change  that  rate.  While  the  quality  of  the  work  must 


§24 


SHOP  HINTS. 


31 


always  be  the  first  consideration,  the  time  element  should 
never  be  disregarded.  Thus,  an  apprentice  may  think, 
because  his  pay  is  small,  that  only  a small  amount  of  work 
should  be  expected  of  him,  and,  hence,  may  conclude  that 
he  will  increase  his  speed  when  he  becomes  a journeyman  or 
receives  a higher  compensation.  He  should  consider,  how- 
ever, that  the  money  he  receives  is  the  smallest  part  of 
his  compensation,  and  that  the  trade  he  is  learning,  the 
manual  and  mental  training,  and  the  experience  that  he  is 
receiving  form  the  greater  part.  Such  a boy  may  learn  to 
do  a piece  of  work  well,  but  is  not  likely  to  receive  the  high- 
est rate  of  compensation  when  he  becomes  a journeyman, 
since  his  rate  of  speed  generally  remains  abnormally  low. 

37.  Standard  of  Quality  and  Speed  of  Work. — In 

performing  a certain  operation  on  a piece  of  work,  or  in  fact 
in  doing  any  kind  of  work,  it  must  always  be  remembered 
that  work,  and,  consequently,  the  value  of  the  producer,  is 
measured  by  two  different  standards,  the  mechanical  and  the 
commercial.  The  mechanical  standard  measures  the 
degree  of  skill  with  which  the  work  is  executed  and 
the  excellence  of  the  design ; in  other  words,  it  is  a measure 
of  the  quality  of  the  work.  The  commercial  standard 
takes  account  of  the  labor  cost,  and  the  person  that  reduces 
this  factor  to  the  lowest  limit  Compatible  with  the  degree  of 
mechanical  excellence  that  the  nature  and  purpose  of  the 
work  requires,  is  the  one  that  will,  and  properly  should, 
receive  a higher  compensation  for  his  services  than  the 
person  that  can  do  a good  job  only  when  he  is  given  an 
unlimited  amount  of  time. 

An  old  proverb  states  that  “what  is  worth  doing  at  all  is 
worth  doing  well.”  This  proverb  is  applicable  to  many 
cases  and  conditions,  but  a blind  adherence  to  it  is  liable  to 
be  a serious  detriment  to  a person  engaged  in  commercial 
work.  For  such  a person  the  proverb  might  profitably  be 
changed  to  read  “ what  is  worth  doing  at  all  is  worth  doing 
as  well  as  the  circumstances  of  each  case  require.”  That 
is,  the  quality  of  the  workmanship  should  be  suited  to  the 


32 


SHOP  HINTS. 


§24 


purpose  to  which  the  work  is  to  be  put,  and  unnecessary 
refinements  and  ornamentation  that  neither  add  to  appear- 
ance nor  usefulness  should  be  omitted. 


THE  SCRAP  HEAP. 

38.  Lessons  From  the  Scrap  Heap. — The  final  rest- 
ing place  of  all  the  metallic  appurtenances  of  the  machine 
shop,  smith  shop,  and  boiler  shop  is  the  scrap  heap.  In 
this  universal  receptacle  are  found  all  kinds  of  metallic 
objects  in  all  conditions,  from  the  new  special  machine  left 
on  the  builder’s  hands  by  some  turn  of  fortune  to  that  mass 
of  metal  so  thickly  coated  with  rust  or  grease  that  only  a 
cold-chisel  test  will  determine  whether  it  is  brass,  steel,  or 
lead.  A scrap  heap  is  a kind  of  shop  barometer,  telling  in 
its  own  mute  fashion  of  the  general  shop  management  of  the 
place  and  of  the  use  or  misuse  of  materials  in  other  places. 
A scrap  heap  represents  employed  capital,  and  for  this  reason 
it  should  be  run  through  the  cupola  or  furnace  as  soon  as 
possible,  and  thus  be  reduced  to  available  assets. 

Many  valuable  lessons  can  be  learned  by  an  intelligent 
inspection  of  the  various  pieces  to  be  found  in  a scrap  heap. 
The  undue  weakness  of  compotent  parts  of  machinery  is 
here  shown  by  the  presence  of  the  broken  parts,  and  a care- 
ful inspection  of  the  appearance  of  the  breaks  will  not  only 
show  where  the  parts  need  strengthening,  but,  also,  whether 
or  not  the  break  was  due  to  an  abuse  of  the  machine.  The 
presence  of  a large  number  of  broken  small  tools  of  the 
same  kind  may  safely  be  considered  as  an  indication  of  a 
defect  in  their  design,  although  in  isolated  cases,  especially 
in  shops  where  much  unskilled  labor  is  employed,  it  may 
indicate  bad  management  on  the  part  of  some  responsible 
person. 

39.  Patching  Chipped  Castings. — In  the  handling 
of  heavy  castings  it  frequently  happens  that  chips  or  flakes 
are  knocked  off  by  accidental  collisions  with  other  work. 
While  these  may  not  weaken  the  machine  appreciably,  they 
are  unsightly,  and  for  the  sake  of  appearances  such  defects 


SHOP  HINTS. 


33 


§ 24 

should  be  remedied.  There  are  compounds  on  the  market 
especially  prepared  for  this  work.  The  dry  compound  is 
moistened  until  it  has  the  consistency  of  putty,  and  is  then 
pressed  over  the  defacement  and  allowed  to  harden.  When 
once  hard,  it  adheres  firmly  and  may  be  filed  precisely  like 
iron.  It  then  presents  a metallic  surface. 

40.  Brazing  Broken  Castings.  — Commonly,  a 
broken  iron  casting  is  consigned  to  the  scrap  heap,  but  it  is 
possible  in  many  cases  to  prevent  this  loss  by  brazing  the 
broken  parts  together.  This  is  done  by  using  a patented 
brazing  composition  or  flux  called  “ Borafix,”  which  is  spread 
evenly  over  the  fractured  surfaces.  These  are  then  placed 
together  properly,  and  brought  to  a cherry-red  heat,  which 
melts  the  flux.  Spelter  or  brazing  material  is  added,  after 
which  the  piece  is  allowed  to  cool  in  the  air.  This  method 
recommends  itself  in  cases  where  the  castings  are  not  sub- 
jected to  extraordinary  strains  and  are  not  excessively  large. 
The  process  is  a comparatively  new  one,  but  it  has  a valu- 
able place  in  the  work  of  the  shop.  Castings  should  not, 
however,  be  repaired  in  this  way  or  in  any  other  when  it 
will  cost  more  to  do  the  repairing  than  it  would  to  make 
a new  casting. 

41.  Repairing  a Leaky  Cylinder. — To  repair  a leaky 
cylinder  caused  by  open-grained  iron,  make  a saturated  solu- 
tion of  hydrochloric  acid  and  iron  drillings,  and  pour  this 
into  the  cylinder,  or  wash  the  interior  of  the  cylinder  with 
the  solution.  Next  apply  ammonia  water,  and  then  steam 
or  air  pressure,  which  will  drive  the  iron  hydroxide  into 
every  pore  of  the  cylinder  walls.  When  dry,  the  cylinder 
will  be  steam-tight. 


SHOP  HINTS. 

(PART  2.) 


LUBRICANTS. 


INTRODUCTION. 

1.  Two  Uses  of  Lubricants. — A lubricant  may 

serve  for  either  one  of  two  entirely  different  purposes,  and 
should  consequently  be  selected  accordingly.  In  practice,  a 
lubricant  is  used  either  in  order  to  reduce  the  friction  between 
two  bodies,  one  of  which  moves  on  the  other,  or  in  order  to 
carry  away  the  heat  generated  by  a cutting  operation. 


LUBRICANTS  FOR  REDUCING  FRICTION. 

2.  Selecting  a Lubricant. — A lubricant  reduces  fric- 
tion by  interposing  itself  in  the  form  of  a thin  film,  which 
may  be  considered  as  being  composed  of  a large  number  of 
minute  globules,  between  the  rubbing  surfaces  of  the  mov- 
ing bodies.  These  globules  act  as  rollers  or  balls,  and  con- 
vert the  sliding  friction  into  a rolling  friction  to  an  extent 
depending  on  their  deformation  under  the  load  they  carry. 
The  deformation  of  the  globules  of  the  lubricant  depends  on 
its  consistency,  and  is  greater  for  a thin  lubricant  than  for  a 
heavy  thick  one.  For  this  reason  a thick  oil  should  be 
selected  for  heavy  pressures,  while  for  light  pressures  a thin 
oil  may  be  used.  The  contact  between  the  rubbing  surfaces 
must  also  be  duly  considered  in  connection  with  the  selec- 
tion of  a lubricant,  and  one  used  that  is  fluid  enough  to  flow 

§ 24 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


36 


SHOP  HINTS. 


§ 24 

in  between  the  surfaces.  Thus,  in  machine  tools  and  fine 
machinery,  the  rubbing  surfaces  are  usually  fitted  very 
closely  to  each  other,  and  hence  fluid  mineral  oil  having 
sufficient  body  to  last  a reasonable  length  of  time  must 
generally  be  used. 

3.  Oil  for  General  Shop  Use. — For  general  shop  use, 
a mineral  oil  having  considerable  body  is  well  adapted.  It 
should  be  thin  enough  to  run  freely  through  the  oil  holes 
and  oil  channels  of  bearings.  Animal  oils  are  generally 
objected  to  on  account  of  the  fact  that  decomposition  by 
age  is  liable  to  develop  fatty  acids  that  attack  most  metals. 
Furthermore,  animal  oils  are  very  liable  to  gum,  i.  e.,  some 
of  their  constituent  parts  will  collect  into  a sticky  mass  and 
close  the  oil  channels  of  bearings.  All  oil  intended  for 
lubrication  should  be  entirely  free  from  grit.  By  examining 
a drop  of  the  oil  with  a strong  magnifying  glass,  its  presence 
is  readily  discovered. 

4.  Cylinder  Oil. — A special  grade  of  heavy  oil  known 
to  the  trade  as  cylinder  oil,  is  intended  to  be  used  for 
the  lubrication  of  parts  subjected  to  fairly  high  temper- 
atures, as  the  valves  and  pistons  of  steam  engines.  It  has 
the  property  of  standing  considerable  heating  without  vola- 
tilizing or  being  decomposed.  Owing  to  its  heavy  body,  it 
is  used  sometimes  for  bearings  subjected  to  heavy  pressures. 

r>.  Grease. — For  very  heavy  work  and  relatively  low 
rubbing  speeds,  one  of  the  many  forms  of  manufactured 
grease  is  frequently  used.  The  bearings  must  then  be  fitted 
loosely  enough  to  admit  the  grease.  The  great  body,  which 
is  the  characteristic  feature  of  a grease,  prevents  its  being 
crushed  or  squeezed  out  by  the  weight  of  the  moving  parts. 

G.  Grease  for  Rail  Bearings. — Grease  of  the  best 
quality  may  be  used  to  advantage  in  putting  ball-bearing 
work  together,  when  difficulty  is  experienced  in  keeping  the 
balls  in  place  while  assembling  the  bearing.  The  ball  races, 
or  seats,  are  filled  with  the  grease  and  the  balls  are  then 
pressed  into  it.  The  grease  will  hold  the  balls  in  place  while 


§24 


SHOP  HINTS. 


37 


the  parts  are  being  put  together,  and  will  serve  to  lubricate 
them  for  a long  time  afterwards.  This  is  a very  convenient 
aid  in  assembling  the  ball  bearings  of  the  pneufnatic  drilling 
machines  now  so  commonly  used  in  large  shops,  and  also  of 
bicycles. 

7.  Grease  for  Shafting. — Bearings  of  shaftings  and 
machines  that  are  subject  to  great  wear  and  are  not  at  all 
times  under  the  eye  of  the  attendant,  or  easily  within  reach, 
and  hence  are  liable  to  run  dry  with  the  ordinary  methods 
of  oiling,  are  provided  for  in  the  following  manner:  Grease 
cups  are  screwed,  or  grease  pockets  are  cast,  on  places  where 
bearings  are  liable  to  heat;  these  are  filled  with  a grease  that 
will  not  melt  at  the  ordinary  temperature  of  the  bearing, 
but  as  the  bearing  becomes  warm,  this  grease  melts  and 
runs  down  through  the  oil  holes  to  the  surfaces  needing 
lubrication. 

8.  Light  Oils  for  Cleaning  Bearings. — Refined 
petroleum  (also  called  kerosene,  coal  oil,  or  paraffin 

oil,  in  different  localities)  and  mineral  sperm  oil  are 
among  the  most  fluid  commercial  oils,  and  will  flow  into 
smaller  spaces  than  heavier  oils ; both  have  the  disadvantage, 
however,  that  they  lack  body,  i.  e.,  they  evaporate  quickly, 
and  consequently  are  of  little  value  as  a lubricant.  They 
are  of  great  value  however  in  cleaning  rubbing  surfaces,  as 
they  will  dissolve  or  thin  down  almost  any  heavier  oil,  and 
can  be  used  for  cleaning  bearings,  etc.,  where  it  is  suspected 
that  the  oil  channels  have  become  clogged  by  the  gumming 
of  the  regular  oil  that  is  used.  In  such  a case,  a copious 
and  constant  supply  of  kerosene  or  mineral  sperm  oil  may  be 
applied  to  the  bearing  until  the  oil  comes  out  clear;  it  must 
then  immediately  be  followed  by  a copious  application  of 
the  heavier  oil  generally  used  for  lubrication,  in  order  to 
prevent  any  cutting  of  the  rubbing  surfaces  owing  to  their 
becoming  dry  through  the  rapid  evaporation  of  the  light  oil. 

f).  Thinning  Oils. — The  lighter  oils  can  often  be  used 
advantageously  for  thinning  down  the  heavier  oils  in  order 
to  make  a grade  suitable  for  some  special  purpose.  Most  of 


38  SHOP  HINTS.  § 24 

the  lighter  oils  are  quite  inflammable,  and  consequently  due 
care  must  be  taken  to  prevent  their  ignition. 

1 O.  Volatile  Oils. — Benzine,  naphtha,  and  tur- 
pentine are  used  considerably  in  shops  for  cleaning  pur- 
poses ; these  oils  evaporate  very  rapidly  and  form  vapors  that 
are  highly  inflammable.  If  these  vapors  are  mixed  with  air 
in  certain  proportions,  they  form  explosive  mixtures  that 
need  but  a spark  to  ignite  them.  For  this  reason,  great 
care  should  be  taken  not  to  have  a naked  light  or  any  fire 
close  to  a place  where  any  of  these  volatile  oils  are  stored  or 
used. 

11.  Graphite. — The  mineral  substance  known  tech- 
nically as  graphite,  and  in  shop  parlance  as  black  lead, 
or  plumbago,  forms  an  excellent  lubricant,  which  when 
ground  fine  may  be  used  either  dry  or  may  be  mixed  with 
some  fluid  lubricant  or  grease  to  a consistency  considered 
suitable  for  the  work.  Graphite  is  one  of  the  most  refrac- 
tory substances  known;  this  fact  makes  it  an  invaluable 
lubricant  for  bearings  subjected  to  high  temperatures.  Its 
lubricating  qualities  at  all  temperatures  are  so  high  that  it 
forms  a very  valuable  addition  to  almost  any  oil. 

12.  Curing  Hot  Bearings. — A bearing  will  get  hot 
by  reason  of  friction  due  to  an  insufficient  or  interrupted 
supply  of  the  lubricant,  or  by  reason  of  the  journal  fitting 
so  closely  that  the  lubricant  cannot  pass  between  the  rubbing 
surfaces.  The  first  thing  to  do  when  a bearing  gets  hot  is 
to  supply  it  with  a liberal  quantity  of  oil,  repeating  the  appli- 
cation frequently  until  the  bearing  commences  to  cool.  If, 
the  bearing  becomes  so  hot  that  it  smokes  before  it  is  dis- 
covered, and  it  is  not  advisable  to  stop  the  machine,  water 
may  be  turned  on  the  bearing,  pouring  it  down  the  oil  hole, 
or  playing  a hose  on  it  until  it  is  cool.  When  a hot  bearing 
is  discovered,  the  cap  may  be  slacked  back  somewhat  so  as 
to  allow  a free  circulation  of  the  lubricant.  As  soon  as  the 
bearing  is  cool,  a copious  and  constant  supply  of  oil,  which 
may  have  some  graphite  mixed  with  it,  should  be  provided 
and  the  results  noted.  If  the  bearing  refuses  to  keep  cool 


§24 


SHOP  HINTS. 


39 


after  this,  it  generally  shows  that  the  rubbing  surfaces  are 
in  such  a bad  condition  as  to  need  refitting. 

If  the  hot  bearing  is  rigid,  i.  e.,  not  self-adjusting  to  the 
shaft,  observe  if  one  end  is  hotter  than  the  other;  also  test 
the  shaft  for  alinement,  as  the  heating  of  the  bearing  may 
not  be  caused  by  a defect  in  the  hot  box,  but  by  the  bearing 
next  to  it  getting  out  of  line,  thus  bringing  all  the  load  on 
one  end  of  the  bearing  that  is  heating. 

13.  Oil  Holes  and  Oil  Channels. — Various  means 
are  provided  to  make  sure  that  the  lubricant  reaches  the 
place  or  surface  it  is  intended  to  cover.  In  the  first  place, 
oil  holes  are  drilled  through  the  metal  from  the  high  side  so 
that  the  oil  will  reach  its  proper  place  by  gravity.  The 
size  of  the  oil  holes  should  vary  with  the  kind  of  lubricant 
that  is  to  be  used,  drilling  small  holes  in  small  work  and  for 
a fluid  lubricant,  and  larger  ones  as  the  density  of  the  oil 
and  the  length  of  the  hole  increase.  Bearings  that  are  not 
easily  reached  must  have  tubing  or  pipe  run  to  them  as 
directly  as  possible;  this  oil  piping  should  be  supplied  with 
fittings  that  allow  it  to  be  easily  taken  down  and  cleaned. 

14.  Cutting  Oil  Channels. — Oil  channels  should  be 
cut  so  as  to  distribute  the  oil  over  the  whole  length  of  the 
bearing;  also,  such  other  channels  should  be  provided  as 
may  be  needed  to  insure  an  even  distribution  of  the  lubri- 
cant. In  order  to  insure  thorough  lubrication,  the  oil  chan- 
nels must  have  a liberal  width  and  must  be  deep  enough  so 
as  not  to  become  filled  too  rapidly  with  the  impurities  some 
lubricants  contain.  Furthermore,  the  direction  in  which 
the  oil  channels  run  from  the  point  of  supply  (the  bottom  of 
the  oil  hole)  should  be  the  same  as  the  direction  of  rotation 
of  the  journal,  in  order  that  the  latter  may  tend  to  draw  in 
the  oil  rather  than  to  repel  it.  A lubricant  will  not  flow  up 
hill  any  more  than  any  other  liquid;  hence,  the  lubricant 
should  always  be  applied  at  the  highest  point  permitted  by 
circumstances. 

1 5.  Special  Methods  of  Oiling. — Small  planers  have 
their  ways  oiled  by  hand  whenever  they  show  any  indication 


40 


SHOP  HINTS. 


24 


of  becoming  dry.  Large  planers  are  usually  provided 
with  means  for  a constant  lubrication,  as,  for  instance,  oil 
wells  cored  out  in  several  places  in  the  ways.  These  wells 
are  filled  with  oil  that  is  delivered  to  the  ways  by  conical 
brass  rollers  that  are  pressed  against  the  V’s  of  the  platen  by 
springs.  This  method  of  oiling  is  perfect  as  long  as  reason- 
able care  is  used  to  prevent  an  accumulation  of  dust  and 
dirt  in  the  oil  wells,  which  would  finally  interfere  with  the 
free  action  of  the  rollers. 

16.  Use  of  Waste.  — Enough  lubricant  should  be 
applied  to  machinery,  and  in  the  right  place,  to  insure  a 
thorough  lubrication;  and  any  dirty  surface  should  be  wiped 
off  so  as  to  keep  the  machine  as  neat  as  possible.  Waste  is 
generally  used  for  this  purpose;  when  dirty,  it  is  often 
thrown  on  the  floor  or  into  out-of-the-way  places;  or  it  is 
left  lying  on  the  work  or  machine.  This  is  an  extremely 
bad  practice,  being  not  only  wasteful  and  dirty,  but  also 
very  dangerous  on  account  of  the  liability  of  the  waste  to 
take  fire  either  from  spontaneous  combustion  or  otherwise. 

1 7.  Disposition  of  Greasy  Waste. — All  waste  or 
greasy  material  of  this  sort  should  be  put  into  sheet-iron 
tanks  or  barrels  located  at  convenient  points  throughout  the 
shop.  These  tanks  should  be  made  of  heavy  galvanized 
iron  or  steel,  and  should  have  legs  to  keep  their  bottoms  2 
or  3 inches  above  the  floor.  They  should  be  riveted  together, 
instead  of  being  soldered,  so  that  if  the  material  in  them 
does  get  on  fire,  they  will  not  come  apart  and  set  fire  to  the 
building.  A good  tight-fitting  cover  should  be  kept  on  the 
tank  at  all  times,  so  that  if  fire  does  start  in  the  waste,  it 
will  be  smothered  before  gaining  much  headway.  These 
tanks  should  be  taken  out  and  emptied  at  stated  times. 

In  some  shops  the  dirty  waste  is  washed  and  used  again. 
The  cleaning  is  done  by  putting  it  into  a tank  of  water  with 
soda,  cheap  soap,  or  some  washing  compound,  and  boiling  it 
for  a few  hours  by  either  live  or  exhaust  steam  entering  the 
tank  through  a suitably  arranged  pipe. 


SHOP  HINTS. 


41 


§ 24 

LUBRICANTS  FOR  CARRYING  AWAY  HEAT. 

I 8.  Reason  for  Removing  Heat  Generated. — The 

cutting  speed  of  a tool  may  often  be  considerably  increased 
by  the  application  of  some  kind  of  lubricant,  such  as  oil  or 
water.  When  oil  is  used,  it  reduces  the  friction  between  the 
shaving  and  the  face  of  the  tool,  and  thus  reduces  the  heat- 
ing. If  a sufficient  quantity  is  used,  it  also  carries  off  a 
great  deal  of  the  heat  generated  by  the  cutting  operation 
and  keeps  the  tool  from  getting  as  hot  as  it  otherwise  would ; 
consequently,  it  is  possible  to  increase  the  .cutting  speed 
without  overheating  the  cutting  edge. 

1 9.  Lubricants  for  Steel  and  Wrought  Iron. 

The  best  lubricants  for  cutting  steel  or  wrought  iron  are 
the  best  grades  of  lard  oil  and  sperm  oil.  One  of  these  oils 
should  be  used  for  all  tapping  or  reaming  operations.  For 
turning  shafts,  soda  water  is  used,  or  in  some  cases  a mixture 
of  soft  soap  and  water.  Soda  water  is  an  excellent  medium 
for  absorbing  heat;  the  soda  also  keeps  the  water  from  rust- 
ing the  machines  or  the  work.  Soft  soap  dissolved  in  water 
is  used  in  some  shops  instead  of  soda  water  and  possesses 
some  lubricating  quality.  When  a finishing  cut  is  taken  on 
soft  iron  or  steel  with  a keen  tool,  and  a supply  of  water 
is  kept  on  the  tool,  a very  bright  smooth  surface  is  produced. 
Such  a cut  is  called  a zvater  cut;  some  kinds  of  work  are 
thus  finished  with  sufficient  smoothness  to  make  polishing 
unnecessary. 

20.  Conditions  Under  Which  Lubricants  Should 

Not  Be  Used. — Cast  iron  is  usually  worked  dry.  The  dirt 
caused  by  mixing  fine  cast-iron  turnings  with  oil  or  water  on 
the  machine  is  an  objectionable  feature  that  more  than  over- 
balances the  increased  cutting  speed  that  might  be  obtained. 
Furthermore,  it  is  difficult  to  take  a light  cut  on  cast  iron 
when  it  is  oily.  The  oil  soaks  into  the  surface  of  the  iron 
for  a short  distance  and  seems,  to  form  a skin  that  is  not 
easily  broken.  If  the  cut  is  deeper  than  a finishing  cut,  the 
oil  on  the  surface  will  not  impede  the  cutting.  Brass,  copper, 
and  Babbitt  metal  are  generally  cut  without  a lubricant, 
C.  5.  I11.-26 


42 


SHOP  HINTS. 


§ 24 

although  it  is  becoming  the  practice  to  flood  work  composed 
of  these  metals  with  lard  oil  in  automatic  screw-machine 
work  so  as  to  reduce  friction  and  increase  the  life  of  the 
tools. 

21.  A Cheap  Lubricant  for  Tools. — For  some  classes 
of  work,  a cheap  and  satisfactory  lubricant  may  be  made  by 
combining  oil  with  other  ingredients.  There  are  many  such 
mixtures  in  use  in  which  an  oil  is  first  thinned  down  by 
mixing  it  with  a cheap  liquid-like  soda  water,  and  then  add- 
ing some  ingredient  that  will  give  body  to  the  lubricant,  i.  e., 
thicken  it  enough  to  make  it  somewhat  adhesive.  A good 
mixture  may  be  made  by  mixing  together  \ pound  of  sal 
soda,  -J  pint  of  lard  oil,  4 pint  of  soft  soap,  and  enough  water 
to  make  10  quarts.  This  should  be  boiled  ^ hour  and  well 
stirred.  When  cool,  ft  is  ready  for  use.  This  mixture  can 
easily  be  handled  by  a pump,  and  is  quite  satisfactory  for 
general  use. 

22.  A Pipe  System  of  Lubrication. — When  a large 
number  of  machine  tools  are  kept  busy  on  work  where  con- 
stant lubrication  is  deemed  essential,  it  is  often  convenient 
to  place  the  tank  containing  the  lubricant  in  some  warm  out- 
of-the-way  place,  as  in  the  boiler  room.  A system  of  piping 
having  branch  pipes  leading  to  the  different  machines  may 
then  be  laid  through  the  shops.  A force  pump  of  some 
kind  should  be  placed  near  the  tank  and  have  its  suction 
pipe  connected  to  it,  while  its  discharge  pipe  connects  with 
the  pipe  system.  All  the  drippings  may  be  automatically 
returned  to  another  tank  near  the  first  through  a separate 
pipe  system  so  arranged  that  they  will  flow  back  by  gravity. 
By  grouping  together  all  the  machines  requiring  lubrication, 
the  piping  system  can  be  made  relatively  inexpensive.  The 
placing  of  the  tank  in  the  boiler  room  is  especially  con- 
venient in  the  case  of  mixtures  that  require  boiling,  since  a 
steam  coil  can  then  be  placed  in  the  tank  at  small  expense. 

Another  arrangement  of  the  pipe  system  has  the  supply 
tank  located  at  a height  that  will  cause  the  lubricant  to  flow 
to  the  machines  by  gravity,  and  the  pump  is  used  to  raise  it 


SHOP  HINTS. 


43 


§ 24 

from  the  lower  to  the  upper  tank.  The  oil  should  always 
pass  through  a strainer  or  a filter  before  being  used  again. 

23.  Lubricants  in  Cutting  Babbitt  Metal. — Bab- 
bitt metal  may  be  worked  dry  in  most  cases,  but  when 
bushings  of  this  material  are  being  bored  in  the  lathe  or 
when  boxes  are  machined  in  position,  it  is  often  found  that 
a lubricant  is  necessary.  This  is  especially  true  of  bushings 
that  are  being  bored  in  the  lathe,  since  the  chip  has  a ten- 
dency to  wind  around  the  boring  tool  and  form  a compact 
ball.  Boxes  that  have  been  bored  and  are  to  be  reamed  will 
sometimes  be  scored  or  roughened  in  the  reaming  if  the 
work  is  done  dry.  Lard  oil  is  sometimes  used  in  working 
Babbitt  metal,  but  a copious  supply  of  kerosene  oil  will  give 
far  better  results  than  any  other  lubricant. 

24.  Lubricants  for  Drilling  Rawhide. — It  is  some- 
times necessary  to  drill  rawhide  with  a twist  drill ; this,  in 
general,  will  be  found  a trying  and  tedious  job,  on  account 
of  the  clogging  up  of  the  flutes  of  the  drill  when  the  drilling 
is  done  dry.  If  a cake  of  ordinary  laundry  soap  is  held 
against  the  drill  every  little  while,  however,  no  trouble  will 
be  experienced.  The  drill  should  be  run  quite  fast  for 
drilling  rawhide. 

25.  Turpentine  as  a Lubricant. — It  is  sometimes 
necessary  for  fitters  who  are  working  on  cast-iron  work  to 
use  a lubricant,  other  than  the  marking  material,  when  they 
are  rubbing  two  parts  together  in  order  to  obtain  bearing 
marks.  Oil  will  prevent  the  seizing  and  cutting  of  the  sur- 
faces, but  it  will  leave  no  bearing  marks,  and,  besides,  it  will 
interfere  with  the  scraping.  Turpentine  may  be  used  freely 
on  such  work,  however,  instead  of  oil,  and  will  prove  bene- 
ficial rather  than  otherwise. 


PREVENTING  WASTE  OF  LUBRICANTS. 

26.  The  Oil  Separator* — Shops  in  which  a great  deal 
of  screw-machine  work,  milling,  and  tapping  of  wrought 
iron  or  steel  is  done,  use  correspondingly  large  quantities  of 


44 


SHOP  HINTS. 


§24 


oil  to  lubricate  the  cutting  tools.  This  oil  becomes  mixed 
with  the  cuttings  or  chips  from  the  work,  and  while  most  of 
this  oil  can  be  drained  off,  a large  amount  adheres  firmly  to 
the  chips  and  is  usually  thrown  away.  Much  of  this  oil  may 
be  saved  by  collecting  the  oily  chips,  and  running  them 
through  a centrifugal  separator.  This  separator  consists 
of  a circular  tank  that  is  open  at  the  top  and  is  provided 
with  a cock  in  the  bottom,  in  order  to  allow  the  extracted 
oil  to  be  drained  off.  A vertical  spindle  passing  up  through 
the  center  of  the  tank  carries  a strong  conical  steel  pan  pro- 
vided with  an  equally  strong  cover  that  is  held  on,  when  in 
use,  by  a locknut.  The  edge  of  the  pan  has  small  openings 
for  the  escape  of  the  oil.  A pulley  is  provided  on  the  lower 
end  of  the  spindle  to  drive  the  extracting  pan,  and  is  belted 
to  an  overhead  countershaft. 

The  pan  is  filled  with  the  oily  chips,  th£  cover  securely 
fastened,  and  the  machine  started  slowly  and  allowed  to 
come  up  to  its  full  speed,  which  should  give  about  7,000  feet 
per  minute  at  the  periphery.  The  oil  is  thrown  from  the 
chips  by  the  centrifugal  force  and  finds  its  way  out  through 
the  small  openings  in  the  top  edge  of  the  pan.  As  the  oil  flies 
from  the  pan  it  is  caught  by  the  wall  of  the  tank  and  flows 
down  to  the  oil  well. 

27.  The  Oil  Filter. — Oil  that  has  been  used  over  a 
number  of  times  is  liable  to  be  filled  with  very  fine  chips 
that  separators  will  fail  to  remove.  Such  oil  may  be  filtered 
through  a regular  oil  filter  ; in  the  absence  of  such  a device, 
blotting  paper  will  be  a fair  substitute.  Some  of  the  heavier 
particles  of  metal  in  the  oil  can  be  gotten  rid  of  by  letting 
the  oil  stand  in  a quiet  place  for  some  time,  when  the  heavy 
foreign  matter  will  settle  to  the  bottom  of  the  vessel.  The 
clear  oil  may  then  be  poured  off  into  another  vessel.  This 
settling  process  will  fail  to  clean  the  oil  as  effectually  as  an 
oil  filter  will  do.  Oil  cleaned  by  the  settling  process  should 
never  be  used  for  lubricating  bearings,  but  only  for  the 
cutting  tools.  An  oil  filter  or  settling  tank  will  not  work 
well  if  kept  in  a cold  place. 


SHOP  HINTS. 


45 


§ 24 


TRANSMISSION  OF  POWER. 


BELTING  ANI)  SHAFTING. 


BELTING. 

28.  Length  of  Belts.— One  of  the  most  common  cal- 
culations in  shop  work  is  that  concerning  the  length  of  belt 
that  is  required  for  a certain  position.  If  the  shafts  and 
pulleys  are  already  in  place,  the  simplest  way  to  find  the 
necessary  length  is  to  stretch  a tape  line  around  the  pulleys 
in  the  position  in  which  it  is  desired  to  place  the  belt  and 
thus  to  obtain  the  length  directly.  In  such  a case,  the 
stretch  of  the  tape  line  is  taken  to  be  the  same  as  that  neces- 
sary for  the  belt. 

However,  in  case  the  pulleys  are  not  in  position,  so  that  a 
tape  line  cannot  be  used,  the  length  of  the  belt  must  be  cal- 
culated, and  this  can  be  done  by  the  following  rule: 

Dule. — To  find  the  length  of  a direct  open  belt , multiply 
one-half  the  sum  of  the  pulley  diameters  by  S\  and  add  to  this 
product  twice  the  distance  between  the  centers  of  the  shafts . 
This  sum  will  be  the  approximate  length  of  the  belt  required. 

The  above  rule,  expressed  as  a formula,  would  read 

* . * (£+*)  + ,4 

in  which  B — length  of  belt  in  inches; 

D — diameter  of  one  pulley  in  inches; 
d — diameter  of  other  pulley  in  inches; 

L — distance  between  centers  of  shafts  in  inches. 

Example. — The  distance  between  the  centers  of  two  shafts  is 
10  feet;  the  diameter  of  the  larger  pulley  is  36  inches  and  of  the 
smaller  pulley  ~28  inches.  What  is  the  length  of  belt  required  ? 

Solution. — The  distance  between  shaft  centers  is  10  ft.,  or  12  x 10 
= 120  in.  Then,  by  the  rule  given, 

(ofi  _i_  OQ\ 

— T — j + 2 x 120  = 3|  x 32  + 2 x 120  = 344  in.  Ans. 


40 


SHOP  HINTS. 


29.  The  approximate  length  of  a crossed  belt  is  given 
by  the  formula 


30.  Arc  of  Contact. — The  arc  on  which  the  belt  touches 
the  pulley  is  called  the  arc  of  contact.  If  it  were  possible 
for  the  belt  to  extend  once  completely  around  the  pulley, 
the  arc  of  contact  would  be  360°.  If  ,the  belt  touches  the 
pulley  along  half  of  its  surface,  the  arc  of  contact  is  180°; 
if  it  touches  the  pulley  along  quarter  of  its  face,  the  arc 
of  contact  is  90°;  and  similarly  for  any  portion  of  surface 
covered  by  the  belt  on  the  pulley. 

To  find  the  arc  of  contact,  stretch  a string  tightly  over 
the  pulleys  in  the  position  the  belt  is  to  occupy.  Then 
take  another  string  and  wrap  it  once  around  the  pulley  and 
cut  it  so  that  the  ends  meet.  The  length  of  this  string 
represents  the  distance  around  the  pulley.  Now  take  a 
third  string  and  hold  one  end  at  the  point  where  the  arc 
of  contact  on  the  pulley  begins,  as  shown  by  the  string 
stretched  over  the  pulleys  representing  the  belt.  Wrap  this 
third  string  around  the  pulley  alongside  the  string  that 
represents  the  belt,  to  the  point  where  the  latter  leaves  the 
pulley.  Cut  the  third  string  at  this  point.  The  length  thus 
cut  off  is  the  distance  covered  by  the  belt  on  the  pulley. 
Then,  the  arc  of  contact  is  equal  to  the  length  of  this  third 
string  multiplied  by  360,  divided  by  the  length  of  the  second 
string,  which  represented  the  distance  around  the  pulley. 

The  above  rule  applies  to  cases  where  the  pulleys  are  in 
position.  If  the  arc  of  contact  is  to  be  taken  from  a draw- 
ing, it  can  be  quickly  found  by  the  use  of  a protractor. 

31.  Effective  Pull. — The  driving  side  of  a belt  is 
always  under  greater  tension  than  the  slack  side.  The 
difference  in  tension  of  the  two  sides  is  the  force  that  tends  to 
turn  the  driven  pulley,  or  the  effective  pull.  The  tension, 
or  pull  in  pounds,  on  the  driving  side  of  the  belt  is  governed 
by  three  things:  the  effective  pull,  the  coefficient  of  friction 
between  the  belt  and  pulley,  and  the  length  of  the  arc  of 


SHOP  HINTS. 


47 


§ 24 

contact.  The  effective  arc  of  contact  is  that  on  the  smaller 
pulley. 

The  effective  pull  that  may  be  allowed  per  inch  of  width 
of  a single  leather  belt  varies  according  to  the  arc  of  contact. 
Table  I gives  the  allowable  effective  pull  per  inch  of  width 
for  different  arcs  of  contact  of  a single  belt. 

TABLE  I. 


ALLOWABLE  EFFECTIVE  BELT  FULL. 


Arc  Covered  by  Belt. 

Allowable  Effective 
Pull  Per  Inch 

Degrees. 

Fraction  of  Whole  Face. 

of  Width. 
Pounds. 

9° 

i = -250 

23.0 

H2i 

ITT  = -3i2 

27.4 

120 

^ = *333 

28.8 

I35 

1 = -375 

31  • 3 

!5° 

T2  = -417 

33-8 

!57i 

it?  = -437 

34-9 

180,  or  over 

i = • 5°° 

38.1 

Table  I enables  one  to  calculate  the  horsepower  that  a 
given  belt  can  transmit,  or  to  find  the  width  of  a belt  required 
to  transmit  a given  horsepower.  The  allowable  effective 
pull  per  inch  of  width  varies  greatly  in  practice;  in  some 
cases  it  is  as  much  as  50  per  cent,  greater  than  that  given 
in  the  table. 

32.  Horsepower. — The  term  horsepower  represents 
a rate  of  doing  work.  If  a man  lifts  a weight  of  100  pounds 
vertically  a distance  of  1 foot,  he  does  100  X 1 = 100  foot- 
pounds of  work.  If  he  lifts  a weight  of  25  pounds  a distance 
of  4 feet,  he  still  does  25  X 4 = 100  foot-pounds  of  work. 

One  horsepower  represents  33,000  foot-pounds  of  work 
done  in  1 minute,  or  550  foot-pounds  per  second.  That  is,  if  a 
belt  has  an  effective  pull, of  55  pounds  and  runs  at  a speed  of 
10  feet  per  second,  then  the  force  of  55  pounds  acts  through 


SHOP  HINTS. 


§24 


48 


a distance  of  10  feet  each  second,  and  the  power  developed 
is  10  X 55  = 550  foot-pounds  per  second,  or  1 horsepower. 

33.  Belt  Speed. — The  speed  at  which  the  belt  runs 
determines  the  horsepower  transmitted.  In  order  to  find 
the  speed  of  any  belt  use  the  following  rule: 

Rule. — Multiply  the  diameter  of  the  pulley  in  inches  by 
3.1Jfl6,  and  this  by  the  number  of  revolutions  per  minute  of 
the  pulley , and  divide  the  product  by  12.  The  result  is  the 
speed  of  the  belt  in  feet  per  minute. 


No  allowance  is  made  in  this  rule  for  the  slip  of  the  belt. 
All  belts  slip  some;  hence  a slip  of  2 per  cent,  is  allowed  in 
most  belting  problems.  Belts  sometimes  run  as  slow  as 

1.000  feet  per  minute,  or  even  slower,  and  a speed  of 

6.000  feet  per  minute  should  never  be  exceeded.. 

34.  Horsepower  of  Belts. — In  order  to  find  the 
horsepower  that  a single  leather  belt  under  given  conditions 
will  transmit,  use  the  following  rule: 


Rule. — Find  the  arc  of  contact  on  the  smaller  pulley  and 
from  Table  I obtain  the  corresponding  effective  pull.  Then 
multiply  together  the  effective  pull,  the  width  of  the  belt  in 
inches , and  the  speed  of  the  belt  in  feet  per  minute,  and  divide 
the  product  by  33,000. 


Example.— A 4-inch  belt  runs  on  two  pulleys  36  inches  in  diameter 

that  make  200  revolutions  per  minute,  (a)  What  is  the  speed  of  the 

belt  ? (b)  What  horsepower  will  it  transmit  ? 

Solution. — ( a ) By  Art.  33,  the  speed  of  the  belt  in  feet  per  minute 

. 36  X 3.1416  X ‘200  , 00,  x,  . » 

is  — = 1,884.96  ft.  per  min.  Ans. 

(b)  As  the  pulleys  are  of  the  same  size,  the  arc  of  contact  is  180°, 
and  from  Table  I the  pull  is  38.1  lb.  From  Art.  34,  the  horsepower  is 
38.1  X 4 X 1,884.96 


33,000 


m 8.7  H.  P.  Ans. 


35.  Width  of  Belts. — In  case  it  is  desired  to  know 
what  width  of  single  leather  belt  is  required  to  transmit  a 
given  horsepower,  the  following  rule  may  be  used : 

Rule. — Multiply  the  horsepozver  to  be  transmitted  by  33,000 
and  divide  this  product  by  the  product  of  the  speed  in  feet  per 


§24 


SHOP  HINTS. 


49 


minute  and  the  effective  pull.  The  result  will  be  the  width 
of  the  belt  in  inches. 

Example. — What  width  of  belt  would  be  required  to  transmit 
16  horsepower  when  the  belt  is  running  at  a speed  of  2,000  feet 
per  minute  and  has  an  effective  pull  of  38.1  pounds  per  inch  of  width. 

Solution. — 38  l^x  ^ ^Oo!)  ~ ^ ^ Tinch  belt  would  be  selected 

for  this  work.  Ans. 


36.  Double  Belts. — Double  belts  are  made  by  cement- 
ing and  riveting  together  two  single  belts,  one  upon  the  other. 
They  are  used  to  transmit  powers  that  would  strain  or  break 
a single  belt.  Naturally,  the  double  belt  is  the  stronger  per 
inch  of  width.  It  is  commonly  assumed  that  a single  belt 
has  T\  the  strength  of  a double  belt  of  equal  width, 
because  the  thickness  of  a double  belt  is  about  T7¥  that  of 
two  single  belts.  Then,  to  find  the  horsepower  that  a double 
leather  belt  will  transmit,  we  have  the  following  rule: 

Rule. — Multiply  together  the  effective  pull , the  width  of 
the  belt  in,  inches,  and  its  velocity  in  feet  per  minute,  and 
divide  the  product  by  -fa  of  33, 000,  or  23,100. 


Example. — How  many  horsepower  will  be  transmitted  by  a double 
belt,  24  inches  wide,  if  the  arc  of  contact  on  the  smaller  pulley  is  150° 
and  the  belt  runs  at  2,500  feet  per  minute  ? 


Solution. — From  Table  I, 


^ 33.8  X 24  X 2,500  or,  Q TT  „ 

then 23.100  ~ 87.8  H.  P. 


the  allowable  effective  pull  is  33.8  lb., 
Ans. 


37.  If  it  is  desired  to. find  the  width  of  a double  leather 
belt  required  for  a certain  horsepower,  use  the  following  rule: 
Rule. — Multiply  the  horsepower  to  be  transmitted  by 
23,100.  Divide  this  product  by  the  product  of  the  velocity  in 
feet  per  minute  and  the  effective  pull  as  found  from  Table  I. 
The  result  is  the  width  in  inches. 


Example. — What  width  of  double  belt  would  be  required  to  trans- 
mit 160  horsepower  with  the  belt  running  at  2,500  feet  per  minute  and 
having  an  arc  of  contact  on  the  smaller  pulley  of  150°  ? 


Solution. — From  Table  I,  the  effective  pull  is  33.8  lb.  per  inch  of 


width ; hence, 


160  X 23,100 
2,500  X 33.8 


43.74  in. 


A 44-inch  belt  would  be  used. 

Ans. 


50 


SHOP  HINTS. 


§24 


SHAFTING. 

B8.  Distance  Between  Bearings. — For  a medium 
steel  shaft  having  no  pulleys  whatever,  and  used  for  trans- 
mission of  power  only,  the  greatest  allowable  distance 
between  adjacent  bearings,  for  shafts  up  to  and  including 
4 inches  in  diameter,  is  given  by  the  following  rule: 

Rule. — Multiply  the  diameter  of  the  shaft  in  inches  by  55 
and  add  55  to  the  product.  The  result  is  the  greatest  allow- 
able distance , in  inches,  between  adjacent  bearmgs. 

For  an  iron  shaft  the  maximum  distance  is  somewhat  less 
than  that  given  by  the  above  rule. 

Example. — What  is  the  greatest  allowable  distance  between  bear- 
ings for  a 3-inch  shaft  of  medium  steel,  used  only  to  transmit  power  ? 

Solution. — According  to  the  rule,  the  maximum  distance  is  (55  X 3) 
+ 55  = 220  in.,  or  18  ft.  4 in.  Ans. 

TABLE  II. 


TURNED-IRON  HEAD-SHAFTS,  BEARINGS  CLOSE  TO 
PULLEYS. 


Revolutions  Per  Minute. 


Diameter  of 
Shaft. 

Inches. 

6o 

80 

100 

150 

200 

250 

300 

Horsepower. 

2. 

.6 

3-4 

4 

•3 

6, 

4 

8.6 

10 

•7 

12.9 

2 

3. 

.8 

5-i 

6 

■4 

9 

.6 

12.8 

16 

.0 

19.2 

2i 

5. 

■ 4 

7-3 

8. 

. 1 

12. 

.0 

16.0 

20, 

.0 

24.0 

2i 

7. 

•5 

10.0 

12 

• 5 

18. 

,0 

25.0 

3i 

.0 

37-o 

2f 

IO. 

.0 

13.0 

16 

.0 

24. 

,0 

32.0 

40. 

.0 

48.0 

3 

13 

.0 

17.0 

20 

.0 

30. 

.0 

40.0 

50, 

.0 

60.0 

3i 

16, 

,0 

22.0 

27 

.0 

40. 

,0 

54-0 

67. 

.0 

81.0 

3i 

20. 

.0 

27.0 

34 

.0 

5i 

,0 

68.0 

35. 

,0 

102.0 

3t 

25. 

,0 

33-0 

42 

.0 

63. 

,0 

84.0 

105, 

.0 

126.0 

4 

30. 

.0 

41.0 

5i 

.0 

76. 

,0 

102.0 

127. 

.0 

153-0 

4i 

43. 

,0 

58.0 

72. 

.0 

108 . 

,0 

144.0 

180. 

,0 

216.0 

5 

60, 

,0 

80.0 

100. 

,0 

150. 

,0 

200.0 

250. 

0 

300.0 

5i 

80, 

.0 

106.0 

133 

.0 

r99 

.0 

266.0 

333. 

.0 

400.0 

SHOP  HINTS. 


51 


§ 24 


39.  For  a countershaft  or  line  shaft  having  many  pul- 
leys, and' consequently  subjected  to  both  bending  and  torsion 
due  to  belt  pulls,  the  distance  from  bearing  to  bearing 
should  be  not  more  than  8 feet. 

For  a head-shaft,  with  a main  driving  pulley  or  gear,  the 
bearings  should  be  placed  very  near  the  driving  wheel  or 
wheels. 

40.  Horsepower  and  Size  of  Shafting. — The  horse- 
power that  a shaft  of  given  size  will  safely  transmit  depends 
on  its  duty.  If  it  is  a plain  shaft,  used  to  transmit  power 
from  one  point  to  another  at  a considerable  distance,  with 
no  pulleys  or  gears  at  intermediate  points,  it  will  transmit 
considerably  more  than  a shaft  of  the  same  size  used  as  a 
countershaft  or  line  shaft,  loaded  with  pulleys,  and  still 
more  than  a head-shaft  carrying  a main  driving  pulley 
or  gear. 

TABLE  III. 


COLD-ROLLED  IRON  HEAD-SHAFTS,  BEARINGS  CLOSE  TO 

PULLEYS. 


Diameter  of 
Shaft. 

Inches. 

Revolutions  Per 

Minute. 

6o 

80 

IOO 

150 

200 

250 

300 

Horsepower. 

4 

2.7 

3-6 

4-5 

.'•7 

9 0 

11 

13 

if 

4-3 

5-6 

7-i 

10.6 

14.2 

18 

21 

2 

6.4. 

8.5 

10.7 

16.0 

21.0 

26 

32 

2\ 

9.0 

12.0 

15.0 

23.0 

30.0 

38 

46 

2I 

12.0 

17.0 

21 .0 

31.0 

41.0 

52 

62 

2f 

16.0 

22.0 

27.0 

41.0 

55-o 

70 

82 

3 

21 .0 

29.0 

36.0 

54-0 

72.0 

90 

108 

3i 

27.0  . 

36.0 

45-0 

68.0 

91 .0 

1 14 

136 

3'* 

34-0 

45-0 

57-o 

86.0 

114.0 

142 

172 

3f 

42.0 

56.0 

70.0 

105.0 

140.0 

174 

210 

4 

510 

69.0 

85.0 

128.0 

170.0 

212 

256 

4i 

73-0 

97.0 

121 .0 

182.0 

243.0 

302 

364 

52  SHOP  HINTS.  § 24 

The  horsepower  that  shafting  of  various  sizes  will  safely 
transmit  is  given  in  Tables  II,  III,  IV,  and  V. 

These  tables  may  be  used  to  find  the  horsepower  that  a 
given  shaft  will  transmit,  or  they  may  be  used  to  find  the 
size  of  shaft  required  to  transmit  a given  horsepower. 

TABLE  IV. 


TURNED-IRON  LINE  SHAFTING  WITH  BEARINGS  8 FEET 

APART. 


Revolutions  Per  Minute. 


u laiiicici  yt  l 

Shaft. 

Inches. 

IOO 

125 

!5° 

200 

250 

300 

350 

Horsepower. 

If 

6.0 

7-4 

0 

CO 

11  9 

14.9 

17.9 

20.9 

7-3 

9- 1 

IO.9 

14-5 

18.2 

21.8 

25-4 

2 

8.9 

11 . 1 

13-3 

17.7 

22.2 

26.6 

31 .0 

2l 

10.6 

13.2 

15-9 

21.2 

26.5 

31.8 

37-0 

2i 

12 . 6 

15-8 

19.0 

25.0 

31.0 

38.0 

44-0 

2I 

15-0 

18.0 

22.0 

29.0 

37-o 

44-0 

52.0 

2i 

17.0 

' '21.0 

26.0 

34-0 

43-0 

52.0 

60.0 

2I 

23.0 

29.O 

34-0 

46.0 

58.0 

69.0 

81.0 

3 

30.0 

37-o 

45-0 

60.0 

75-o 

90.0 

105.0 

3l 

38.0 

47.0 

57-0 

76.0 

95-0 

114.0 

133-0 

3| 

47-0 

59° 

71.0 

95-0 

119.0 

143  0 

167.0 

3f 

58.0 

73-o 

88.0 

117.0 

146.0 

176.0 

205.0 

4 

71.0 

89.0 

107.0 

142.0 

0 

CO 

213.0 

249.0 

Example  1. — What  horsepower  will  be  transmitted  by  a turned-iron 
line  shaft  2|  inches  in  diameter,  running  at  250  revolutions  per  minute  ? 

Solution. — From  Table  IV,  for  turned-iron  line  shafting,  we  find 
the  diameter  in.  in  the  first  column.  Following  out  horizontally 
from  2|  until  we  reach  the  column  headed  250  revolutions  per  minute, 
we  find  43.  Therefore,  the  2|-inch  shaft  will  transmit  43  H.  P.  at 
250  rev.  per  min.  Ans. 

Example  2. — Let  it  be  required  to  find  the  horsepower  of  a cold- 
rolled  head-shaft  4 inches  in  diameter,  making  300  revolutions  per 
minute  ? 


§24 


SHOP  HINTS. 


53 


Solution. — In  Table  III,  for  cold-rolled  shafting,  locate  the  diam- 
eter, 4 inches,  in  the  first  column,  and  follow  this  line  horizontally  to 
the  column  headed  300,  where  256  is  found.  The  4-inch  head-shaft 
will  therefore  transmit  256  H.  P.  at  300  rev.  per  min.  Ans. 

Example  3. — What  size  of  cold-rolled  line  shaft  will  be  required  to 
transmit  200  horsepower  at  300  revolutions  per  minute  ? 

Solution. — In  Table  V,  of  cold-rolled  line  shafts,  locate  the  column 
headed  300  rev.  per  min.  Following  down  this  column  to  the 
value  205  H.  P. , which  is  the  nearest  to  200  that  is  given,  we  find  that 
the  corresponding  diameter  of  shaft,  in  the  first  column,  is  3£  in.  Ans. 

TABLE  V. 


COLD-ROLLEI)  IRON  LINE  SHAFTING,  WITH  BEARINGS 
8 FEET  APART. 


Revolutions  Per  Minute. 


Diameter  of 
Shaft. 

Inches. 

IOO 

125 

150 

200 

250 

300 

350 

Horsepower. 

I-g! 

6. 

• 7 

8. 

4 

IO 

1 

13 

• 5 

16.8 

20. 

, 2 

23.6 

If 

8. 

,6 

IO  . 

7 

12 . 

.8 

17 

. 1 

21.5 

25. 

•7 

31 .0 

If 

IO. 

■ 7 

13 

4 

16 

.0 

21 

■5 

26.8 

32. 

, 1 

39-° 

If 

13 

.2 

16. 

5 

19. 

■7 

26. 

■ 4 

32.9 

39  • 

• 5 

46.0 

2 

16. 

0 

20. 

0 

24 

.0 

32 

.0 

40.0 

48. 

.0 

56.0 

19 

.0 

24. 

0 

29 

.0 

00 

.0 

48.0 

57. 

.0 

67.0 

2i 

22  . 

.0 

28. 

0 

34 

.0 

45 

.0 

56.0 

68, 

.0 

80.  O' 

ry  3 
2 8 

27. 

.0 

33- 

0 

40 

.0 

53 

.0 

67.0 

80 

.0 

94.0 

2i 

31 

.0 

39- 

.0 

47 

.0 

62 

.0 

78.0 

93 

.0 

109.0 

ry  3 

2t 

41 

.0 

52. 

0 

62 

.0 

83 

.0 

104.0 

125 

.0 

145-0 

3 

54 

.0 

67. 

.0 

81 

.0 

108 

0 

0 

-t- 

co 

162 

.0 

189.0 

34 

68. 

. 0 

86. 

.0 

io3 

.0 

137 

.0 

172.0 

205 

.0 

240.0 

3i 

85 

. 0 

107 

.0 

128 

.0 

171 

.0 

214.0 

257 

.0 

300.0 

Example  4. — Suppose  it  is  required  to  find  the  size  of  a turned- 
iron  head-shaft  capable  of  transmitting  200  horsepower  at  200  revolu- 
tions per  minute. 

Solution. — In  Table  II,  for  turned-iron  head-shafts,  locate  the 
column  headed  200  rev.  per  min.  Following  down  this  column  to  the 
value  200  H.  P.,  the  corresponding  diameter  of  shaft,  from  the  first 
column,  is  found  to  be  5 in.  Ans. 


54 


SHOP  HINTS. 


§24 


HEAT  INSULATION. 

41.  Lagging  Steam  Cylinders  and  Pipes. — Cylin- 
ders of  steam  engines  and  main  steam  connections  need  to 
be  as  thoroughly  protected  from  the  cold  as  possible,  in 
order  that  the  condensation  of  steam  may  be  reduced  to  the 
lowest  point.  For  this  purpose  the  cylinder  is  often  coated 
with  a cement,  or  mortar,  composed  largely  of  asbestos. 
This  is  mixed,  tempered,  and  applied  to  the  cylinder  in 
much  the  same  manner  that  mortar  is  put  on  by  a mason. 
The  work  is  done  after  the  supports  for  the  lagging  are  in 
place,  and  the  material  is  applied  in  such  thickness  as  not  to 
interfere  with  the  lagging.  The  cylinders  are  generally 
heated  by  steam  when  this  work  is  done,  so  as  to  dry  the 
material. 

Steam  pipes  for  conveying  live  steam  are  protected  in  a 
variety  of  ways.  Sometimes  the  pipe  is  surrounded  with 
wire  netting  of  about  f-inch  mesh,  which  is  held  some  dis- 
tance away  from  the  pipe  by  distance  pieces  that  are  fastened 
to  the  wire  netting  and  butt  against  the  pipe.  Non-con- 
ducting mortar  is  applied  to  this  netting  and  pressed  in  on 
the  pipe;  when  the  pipe  is  outdoors,  it  is  usually  boxed  in 
order  to  further  protect  it.  If  the  pipe  is  indoors,  it  is  often 
lagged  to  match  the  cylinder.  Several  kinds  of  sectional 
covering  are  made  that  are  easily  applied  to  such  pipes,  and 
are  held  in  place  by  clamps  or  straps. 

The  object  of  jacketing  or  covering  cylinders  and  pipes  in 
this  manner  is  to  retain  the  heat,  except  in  refrigerating 
machinery,  where  the  object  is  to  keep  out  the  heat. 

42.  Cutting  and  Fitting  Sheet  Lagging. — Many 
steam-engine  cylinders  are  covered  with  sheet-steel  or  Russia- 
iron  lagging.  This  lagging,  when  possible,  is  cut  to  the  right 
dimensions  and  rolled  into  a cylindrical  form  ; or  it  is  sheared 
to  the  proper  dimensions,  if  the  cylinder  is  to  be  lagged 
square.  There  still  remains  a great  deal  of  fitting  on  the 
sheet,  or  sheets,  which  is  generally  done  by  hand,  but  which 
may  be  done  on  a machine  similar  to  that  illustrated  in 
Fig.  1 ( a ).  This  machine  has  a column  a that  carries  a 


SHOP  HINTS. 


00 


§34 


table  b.  A movable  slide  c working  in  guides  formed  on 
the  column  carries  a cutter  d,  which  is  attached  to  the  slide 
by  the  clamp  e.  The  guide  bar  f has  a slot  in  its  front  side 
in  which  the  cutter  d slides;  it  is  held  in  position  by  a screw 
and  a hand  wheel g.  The  machine  is  driven  by  means  of  the 


belt  //,  and  an  up-and-down  motion  is  imparted  to  the  cut- 
ter d by  means  of  the  crank  i and  rod  j.  Fig.  1 ( b ) is  a 
detail  of  the  square  cutter  used,  in  which  k is  the  cutting 
edge.  The  sheets  to  be  cut  are  laid  on  the  table  and  pushed 
into  the  notch  / ; the  cutter  then  shears  out  a chip  on  the 


5G 


SHOP  HINTS. 


§ 24 

down  stroke.  Fig.  1 (c)  shows  a section  of  the  cutter  in  the 
plane  indicated  by  the  lines  a,  b , c , Fig.  1 ( b ).  Cutters  of  any 
section  may  be  made  for  following  curved  lines  as  well  as 
straight  lines. 

The  lagging  sheets  are  worked  out  on  this  machine  to 
nearly  the  right  form  and  the  remainder  of  the  fitting  is 
done  by  hand.  The  screw  holes  in  the  sheets  are  generally 
drilled  in  a power-driven  machine.  Finally,  the  sheet  is 
clamped  in  place  while  the  holes  are  marked  off  on  the  cylin- 
der or  lagging  frame;  these  are  then  drilled  into  the  sup- 
porting surfaces  on  the  cylinder  or  the  lagging  frame. 


MISCELLANEOUS  DEVICES. 

43.  Boxes,  Pans,  and  Trays. — All  shops  and  manu- 
facturing establishments  doing  small  work  have  more  or  less 
trouble  in  moving  small  parts  from  place  to  place.  This  is 
generally  done  by  using  such  boxes,  kegs,  and  barrels  as 
happen  to  be  at  hand.  These  soon  become  dirty  or  are 
broken,  and  must  then  be  replaced. 

An  excellent  substitute  for  these  makeshift  devices  is 
found  in  the  metallic  articles  illustrated  in  Fig.  2.  The 

one  shown  in  Fig.  2 (a)  is  a 
steel  box  that  can  be  used  in- 
stead of  a wooden  one  for  many 
shop  purposes.  The  pressed- 
steel  pan  illustrated  in  Fig.  2 ( b ) 
may  be  used  instead  of  the 
box,  and  has  the  advantage 
that  it  will  hold  water  or  oil. 
These  pans,  when  not  in  use, 
may  be  stacked  up,  so  as  to 
occupy  very  little  space.  These 
boxes  are  commonly  called  tote  boxes. 

Another  useful  and  cleanly  device  is  the  tray  rack, 
illustrated  in  Fig.  3.  It  consists  of  three  iron  trays,  the 


§24 


SHOP  HINTS. 


57 


upper  one  of  which  carries  a drawer.  For  shop  use,  casters 
are  added  so  that  it  may  be  moved  from  place  to  place.  It 
is  especially  useful 
where  a number  of 
operations  have  to 
b e performed  o n 
pieces  by  different 
machines.  The 
trays  may  be  used 
by  the  machine-tool 
man  to  hold  both 
his  tools  and  work, 
while  the  drawer 
may  contain  his  in- 
dividual tools. 


44.  Keeping 
Machine-Shop 
Tools. — Various 
methods  are  followed  in  caring  for  machine-shop  tools.  In 
the  simplest  method,  the  tools  are  thrown  down  where  used 
and  left  there  until  they  are  wanted  for  another  job,  when 
they  are  hunted  for  until  found,  and  are  then  cleaned  and 
again  made  ready  for  use.  This  method  is  probably  the 
worst  that  could  possibly  be  devised,  and  is  a direct  evidence 
of  mismanagement.  The  modern  and  proper  plan  of  caring 
for  tools  is  to  require  all  tools  to  be  cleaned  by  the  user, 
and  to  be  returned  to  such  a place  as  may  be  designated  for 
their  storage  and  care. 

Tool  rooms  are  built  in  most  shops  for  the  storage  and 
care  of  all  the  tools  used  in  the  place,  or,  if  the  shop  is 
divided  into  departments,  each  head  of  a department  may 
have  his  own  tool  room  and  a man  to  care  for  it,  who,  in 
addition,  also  does  such  other  work  as  he  may  have  time  for. 
The  tool  room  may  be  used  only  as  a storeroom  for  tools,  or 
it  may  be  equipped  with  such  a varied  selection  of  machine 
tools  that  any  tool  or  appliance  needed  on  the  work  may  be 
made  there,  and  tools  and  light  machinery  may  be  repaired. 

C\  S.  III.— 27 


58 


SHOP  HINTS. 


§24 

Large  shops  usually  have,  in  addition  to  the  tool  room,  such 
storerooms  or  vaults  as  may  be  needed  for  the  storage  of 
any  large  and  valuable  jigs,  tools,  or  fixtures  that  are  seldom 
needed,  but  that  require  protection  from  fire.  Tools  should 
be  kept  in  such  a manner  that  they  may  be  gotten  out  and 
returned  in  the  least  time,  and  should  also,  while  in  their 
places,  be  as  well  protected  from  dust  and  rust  as  possible. 

Drawers  are  extensively  used  for  holding  tools,  and  for 
many  purposes  they  answer  admirably.  They  are,  however, 
very  liable  to  be  overloaded,  which  soon  racks  them  to 
pieces.  This  may  be  avoided  by  making  them  extra  heavy, 
or  providing  rollers  for  them  to  run  on.  They  may  also  be 
easily  handled  if  the  sliding  surfaces  are  of  hard  wood  or 
are  metal-faced,  and  the  contact  surfaces  greased  occasion- 
ally with  a good  lubricating  grease.  Drawers  are  used  to 
the  best  advantage  for  tools  that  are  seldom  needed,  but 
require  protection  from  injury  and  dirt. 

Shelves  or  pigeon- 
holes furnish  the  most 
ready  means  of  keep- 
ing tools  that  are  much 
used.  These  should  be 
as  shallow  as  possible 
in  order  that  the  tools 
may  not  be  pushed  in 
out  of  sight,  and  that 
they  may  be  easily 
brushed  out,  or  blown 
out  if  an  air  hose  is 
used  for  cleaning. 
Cupboards  containing 
numerous  shelves  are 
useful  for  special  tools 
that  are  used  less  fre- 
quently than  standard 
ones,  since  the  cup- 
board doors  protect 
them  from  dirt  and  the  atmosphere. 


SHOP  HINTS. 


59 


§24 

The  walls  of  tool  storerooms  are  often  covered  with 
boards,  which  should  be  painted  and  have  hard-wood  pegs 
put  into  them  on  which  to  hang  milling  cutters  and  similar 
tools;  in  some  cases,  nails  are  used  instead  of  the  wooden 
pegs.  A better  method  of  keeping  cutters  is  shown  in 
Fig.  4,  which  consists  of  a cabinet  having  a series  of  shelves  a 
to  which  boards  b are  hinged.  These  boards  are  provided 
with  hooks  c on  which  to  hang  the  cutters.  This  cabinet 
provides  a clean,  convenient,  and  space-economizing  place 
for  a large  number  of  milling  cutters  and  gear-cutters. 

Racks  of  various  kinds  furnish  a convenient  and  clean 
place  for  keeping  a large  class  of  tools,  such  as  pipe  stocks, 
wrenches,  long  taps,  reamers,  drills,  boring  bars,  cutter  bars, 
sockets,  and  other  similar  long  tools,  in  such  a manner  that 
they  are  easily  put  away  or  gotten  out,  and  are  kept  clean 
when  in  their  places.  A rack 
of  this  description  is  shown  in 
Fig.  5.  It  consists  of  four 
uprights  a that* are  braced  by 
wrought-iron  tie-bars  b.  These 
are  held  by  long  bolts  c,  which 
pass  through  the  tie-bars  b at 
each  end,  and  are  surrounded 
by  distance  pieces  d made  of 
iron  pipe. 

Racks  that  are  constructed 
in  the  manner  shown  in  Fig.  5 
may  be  made  7 feet  high  and 
3J  feet  wide  at  the  base,  with 
the  upright  spaced  at  such  dis- 
tances as  will  accommodate  the 
shortest  tools  that  may  be  kept 
on  them.  Light  and  frequently 
used  tools  are  piled  on  the  arms, 
while  less  used  and  heavier  tools  are  placed  on  the  cross- 
pieces b.  These  racks  may  stand  against  the  wall,  but  are 
preferably  placed  on  the  floor  where  they  can  be  reached 
from  all  sides.  Racks  of  special  design  are  usually  provided 


GO 


SHOP  HINTS. 


§24 


for  such  tools  as  ratchets,  tapping  attachments,  air  drills, 
and  other  portable  drilling  and  grinding  fixtures.  Boxes 
are  sometimes  used  for  storing  tools,  and  when  so  used  they 
should  be  plainly  marked;  a convenient  record  should  also 
be  kept  of  their  exact  contents. 

45.  The  Ram. — It  is  sometimes  necessary  when  taking 
old  machinery  apart,  as,  for  instance,  when  trying  to  remove 
an  old  shaft  from  a wheel  or  crank,  to  strike  the  heaviest  blow 
possible.  The  heavy  blow  carries  the  object  struck  before 
it,  while  lighter  blows  will  simply  upset  the  end  of  the  piece 
and  thus  rivet  it  into  place.  When  heavy  sledge  hammers 
are  used  on  light  work,  the  surfaces  hammered  should  be 
protected  by  a piece  of  Babbitt  metal  or  copper  held  or  laid 
on  them. 

Where  heavier  blows  are  required  than  can  be  struck  with 
a sledge,  a ram  is  used.  This  is  a long  bar  of  iron  sus- 
pended at  its  center  of  gravity,  in  order  that  it  may  hang  in 
a horizontal  position,  and  hung  in  front  of  the  piece  to  be 
rammed.  The  rope  suspending  the  ram  is  made  fast  to  an 
overhead  point,  after  which  the  operators  draw  the  bar,  or 
ram,  backwards  as  far  as  possible,  and  then  run  with  it 
toward  the  piece  to  be  struck.  The  ram  is  often  used  when 
a hydraulic  press  is  not  available  or  would  be 
unfit  for  the  work.  Care  should  be  taken  in 
using  the  ram  not  to  upset  the  face  of  the  part 
that  is  being  rammed,  which  will  only  tighten 
the  parts  in  their  places. 

Since  several  men  are  required  to  operate  a 
heavy  ram,  it  is  an  expensive  operation  that 
should  not  be  resorted  to  if  a press  can  be  used. 

46.  A Sectional  Key. — In  shrinking  to- 
gether two  pieces  that  have  key  seats  that  must 
be  in  line  with  each  other,  a device  known  as  a 
sectional  key  may  be  advantageously  used  for 
alining  the  pieces.  One  form  of  this  device  is 
shown  in  Fig.  6.  Two  tapered  side  keys  a and  b, 
having  handles  a ' and  b'  of  suitable  length,  are  placed  into 


m 


SHOP  HINTS. 


61 


§ 24 

the  two  key  seats  of  the  two  parts  that  are  being  shrunk 
together;  and  when  these  parts  are  in  place,  a tapered  cen- 
tered key  c,  with  a long  handle  c' , is  then  driven  in  between 
them,  thus  forcing  the  side  keys  against  the  sides  of  the 
key  seats  and  alining  them.  When  the  work  has  cooled  off, 
the  device  is  removed,  and  the  permanent  key  fitted  and 
driven  home. 


BABBITT  METAL  AND  BABBITTING. 


BABBITT  METAL. 

47.  Composition  of  Babbitt  Metal. — Babbitt 
metal  is  an  anti-friction  alloy  named  after  its  originator, 
who  used  it  in  a form  of  journal-box  that  he  invented.  Bab- 
bitt metal  is  composed  of  tin,  copper,  and  antimony.  The 
proportions  of  these  elements  as  originally  used  are  given  by 
the  best  authorities  as  follows:  For  heavy  duty,  50  parts  tin, 
2 parts  copper,  8 parts  antimony;  or,  96  parts  tin,  4 parts 
copper,  8 parts  antimony;  and  for  light  duty,  50  parts  tin, 
1 part  copper,  5 parts  antimony. 

The  term  Babbitt  metal  is  also  applied  to  a great  number 
of  alloys  on  the  market  that  are  used  to  line  journal-boxes. 
If  the  user  wishes  to  insure  himself  against  the  purchase  of 
worthless  imitations,  he  should  either  make  the  Babbitt 
himself  or  have  it  made  after  correct  specifications  by  a 
reliable  manufacturer. 

The  melting  points  of  these  three  metals  may  be  taken  as 
follows:  Copper,  1,930°  F.  ; antimony,  1,000°  F.  ; tin,  445°  F. 

48.  Making  Babbitt  Metal.- — In  making  Babbitt 
metal,  it  is  necessary  to  melt  the  copper  first,  as  its  fusing 
point  is  higher  than  that  of  either  of  the  other  two  elements  of 
the  compound.  Add  the  antimony  to  the  melted  copper,  and 
then  put  in  about  one-third  of  the  tin.  The  copper  should 
be  covered  with  a layer  of  powdered  charcoal,  to  prevent 
oxidation  and  vaporization  of  the  tin  and  antimony.  Keep 


62 


SHOP  HINTS. 


§ 24 

the  mass  well  stirred  with  a dry  pine  stick;  add  the  remain- 
der of  the  tin,  and  cast  into  small  ingots.  These  usually 
vary  in  weight  from  1 pound  to  10  pounds,  depending  on  the 
quantity  to  be  used  on  the  work. 

It  does  not  necessarily  follow  that  genuine  Babbitt  metal 
is  required  for  all  such  work.  In  fact,  it  should  not  be  used 
in  boxes  for  all  speeds  and  pressures.  The  legitimate  cost 
of  anti-friction  linings  for  journal-boxes  will  vary,  of  course, 
with  the  prices  of  their  constituent  elements,  and  this  cost 
should  be  proportioned  according  to  the  needs  of  the  case. 

From  the  standpoint  of  cheapness,  ease  in  handling,  anti- 
friction properties,  etc.,  lead  would  be  ideal  as  a bearing 
metal.  For  this  reason  it  forms  the  basis  of  a great  number 
of  the  alloys  used  for  lining  journal-boxes,  in  which  other 
metals,  such  as  antimony,  copper,  tin,  and  zinc,  are  added  to 
correct  the  softness  and  the  shrinkage  of  the  pure  lead. 

In  melting  Babbitt,  care  must  be  taken  to  heat  it  slowly. 
Cover  the  surface  of  the  melting  metal  with  powdered  char- 
coal, to  prevent  oxidation  of  the  tin  and  antimony,  and  stir 
with  a dry  pine  stick.  This  stick  serves  as  a guide  to  the 
correct  temperature  of  the  Babbitt,  since  the  molten  metal 
must  not  become  so  hot  as  to  char  the  pine. 

49.  Old  type  metal  makes  an  excellent  bearing  metal  for 
ordinary  work,  in  fact  all  except  heavy  work,  and  for  light 
work  it  will  carry  some  additional  lead.  In  one  case  the 
back  pillow-block  of  a 60-horsepower  engine  babbitted  with 
type  metal,  when  taken  out  after  25  years’  use,  showed  little 
or  no  signs  of  wear. 


BABBITTING. 

50.  Melting  Babbitt  Metal. — Babbitting  is  not 

considered  fine  work,  but  at  the  same  time  it  requires  con- 
siderable experience  and  skill  in  order  to  do  it  well.  The 
amount  of  babbitting  done  in  a shop  varies.  An  occasional 
box  can  be  babbitted  by  metal  melted  in  an  iron  ladle  over  a 
blacksmith’s  fire,  but  in  larger  establishments  the  steady 


SHOP  HINTS. 


6 3 


§ 24 

employment  of  several  men  with  special  fires  and  appliances 
are  often  required.  Babbitt  metal  should  never  be  melted 
over  a blacksmith’s  fire  that  is  to  be  used  for  welding,  for 
if  a little  of  it  gets  into  the  fire,  it  is  likely  to  spoil  the  welds. 
Therefore,  it  is  well  to  have  a fire  set  apart  for  melting 
Babbitt.  A portable  forge  is  especially  useful  for  this  work, 
as  it  can  be  moved  to  the  place  where  the  work  is  to  be  done. 
Coke  is  preferable  to  coal  for  melting  Babbitt  on  account  of 
the  fact  that  it  makes  less  smoke.  Natural  gas  is  an  excel- 
lent fuel  for  this  purpose.  The  ladles  may  be  either  of 
wrought  iron,  steel,  or  cast  iron,  and  should  be  discarded 
when  worn  thin  in  the  bottom,  as  metal  may  be  lost  by  an 
unnoticed  leak.  For  large  work,  the  melting  is  usually  done 
in  either  a cast-iron  kettle  or  a boiler-iron  ladle  set  in  a brick 
furnace.  The  surface  of  the  metal  when  melting  should  be 
covered  with  powdered  charcoal  to  exclude  the  air  in  order  to 
prevent  excessive  oxidization.  The  melted  metal  is  dipped 
out  of  the  melting  pot  in  hand  ladles,  from  which  it  is  poured 
into  the  boxes.  Care  should  be  taken  to  heat  the  ladles  so 
that  they  may  not  chill  the  metal.  A little  powdered  rosin 
should  be  scattered  on  the  surface  of  the  metal  and  the 
metal  stirred  with  a stick  just  before  pouring.  The  rosin 
acts  as  a flux  and  leaves  the  metal  cleaner  and  more  fluid. 

51.  Form  of  Box  for  Babbitting. — The  Babbitt 
metal  in  boxes  or  bearings  is  generally  held  in  place  by 
raised  strips  or  projections  cast  in  the  box,  which  enclose  it 
on  all  sides,  for  the  purpose  of  restraining  the  tendency  of 
the  metal  to  stretch  or  flow  under  the  pressure  or  pounding 
of  the  shaft.  The  strips  should  be  cut  below  the  surface  of 
the  bearing,  so  as  not  to  come  in  contact  with  the  journal. 
In  the  case  of  large  boxes,  dovetail  grooves  are  sometimes 
cast  in  the  surface  of  the  casting  to  aid  the  strips  in  holding 
the  Babbitt,  and  in  some  cases  the  strips  are  omitted,  and 
the  dovetail  grooves  only  are  relied  on  to  hold  the  metal. 
Important  journal-boxes  like  those  in  the  pillow  blocks  of  an 
engine  are  generally  babbitted  from  -J  to  \ inch  smaller  than 
the  finished  bore.  The  metal  is  then  hammered  into  the 


64 


SHOP  HINTS. 


§24 


box  by  using  the  round  peen  of  a hammer  to  either  compress 
or  expand  it  firmly  into  place,  after  which  the  journal  is 
bored  to  the  required  diameter. 

Roller  tools  such  as  are  used  for  expanding  copper  linings 
into  pump  and  hydraulic  cylinders,  as  illustrated  in  Fig.  7, 

may  be  used  to  advantage 
for  expanding  Babbitt  into 
place.  If  the  Babbitt  bearing 
is  chucked  in  a lathe,  the 
tool  (a)  is  used  in  the  tool  post 
and  fed  through  the  work 
after  the  manner  of  a boring 
tool;  or,  if  a boring  bar  is 
used,  the  tool  ( b ) may  be  in- 
serted in  the  bar  or  cutter 
head  and  takes  the  place  of  a boring  tool.  The  feed  and 
speed  of  the  roll  may  be  considerably  faster  than  in  the  case 
of  a boring  tool.  The  surface  to  be  rolled  may  be  lubricated 
with  soda  or  soap,  water  or  oil.  In  the  case  of  small  bear- 
ings, the  metal  is  compressed  by  driving  or  forcing  one  or 
more  polished  steel  drift  plugs  through  the  bearing. 


52.  Mandrels  for  Babbitting. — A mandrel  of  the 
same,  or  approximately  of  the  same  diameter  as  the  shaft 
for  which  the  box  is  made, 
is  placed  in  the  box  when 
the  Babbitt  is  poured. 

The  mandrels  are  often 
made  hollow,  as  shown  in 
Fig.  8,  and  consist  of  a 
cylindrical  portion  a with 
a bar  b across  each  end. 

The  bars  b carry  the  centers  c for  turning  the  mandrel  in  a 
lathe.  The  hollow  mandrel  is  not  only  cheaper  than  a solid 
one,  but  is  also  lighter  to  handle  and  quicker  to  heat  in  case 
it  is  desired  to  warm  it  before  pouring  the  Babbitt.  Man- 
drels are  also  made  of  wood.  Iron  mandrels  should  always 
be  warmed  before  the  metal  is  poured  into  the  box. 


SHOP  HINTS. 


65 


§ 24 

The  mandrels  are  often  made  a little  larger  than  the  jour- 
nal that  is  to  be  used  in  the  box,  both  to  allow  for  the 
shrinkage  of  the  box  and  to  insure  that  the  bearing  will  not 
bind  the  shaft  sidewise;  a box  that  bears  in  the  bottom  is 
less  likely  to  heat  than  one  that  pinches  the  shaft  sidewise. 
Sometimes  paper  is.  wrapped  about  the  journal,  which  is 
used  instead  of  a mandrel;  this  is  not  advisable  except  in 
the  case  of  temporary  work. 

Strips  of  pasteboard  or  wood  may  be  placed  between  the 
mandrel  and  the  strips  that  retain  the  Babbitt  in  the  box  to 
insure  a proper  thickness  of  Babbitt.  To  prevent  the  Bab- 
bitt from  running  out  at  the  ends  and  joints  of  the  box,  the 
openings  should  be  closed  with  clay  or  putty;  care  should 
be  taken  that  they  are  not  too  wet,  as  water  in  the  mold  is 
likely  to  form  steam  and  blow  out  the  metal.  A pouring 
basin  leading  to  the  box  may  also  be  made  of  clay  or  putty; 
large  boxes  are  sometimes  poured  from  several  ladles  simul- 
taneously. In  all  cases,  ample  vents  should  be  left  for  the 
air  to  escape  from  the  box,  and  the  metal  should  be  poured 
at  a low  heat  and  as  rapidly  as  possible.  The  surface  of  the 
mandrel  should  be  slightly  oiled. 

53.  In  case  a large  number  of  boxes  with  machined 
ends  are  to  be  babbitted,  a mandrel  of  the  form  shown  in 
Fig.  9 may  be  used  and  both 
parts  of  the  box  poured  at  once. 

The  mandrel  consists  of  a cyl- 
inder a of  the  required  diameter 
and  length,  with  a disk  b at 
each  end  to  fit  against  the 
machined  ends  of  the  box.  One 
disk  is  held  in  place  by  a cap 
screw  c and  is  removable.  The 
mandrel  is  put  in  position  in 
the  bottom  of  the  box,  and  a liner  d of  pasteboard  or  sheet 
iron  placed  against  each  side  of  it  and  the  cap  bolted  on. 
The  Babbitt  is  poured  through  the  oil  holes  or  slot  in  the 
cap  and  reaches  the  lower  part  of  the  box  through  the 


fig.  9. 


SHOP  HINTS. 


60 


§ 24 


notches  e in  the  liners  d that  are  in  contact  with  the  sides  of 
the  mandrel  a.  The  two  parts  of  the  box  are  separated  by 
driving  a wedge  under  the  cap. 

54.  In  Fig.  10  ( a ) and  ( b ) is  shown  a rig  for  babbitting 
the  pillow  blocks  of  a center-crank  engine.  The  engine 


(b) 

Fig.  10. 


bed  a rests  on  the  parallels  b,  b , which  are  supported  by 
a cast-iron  floor  plate  c.  The  parallel  b under  the  pillow- 
block  d is  set  square  across  the  plate  c and  bolted  to  it,  and 
the  engine  frame  a is  set  to  a center  line  on  the  plate  c.  A 
standard  e rests  on  the  cross-bar  b under  each  end  of 
the  engine  shaft  f The  bottom  of  the  standard  e has  a 


SHOP  HINTS. 


67 


§24 


projection  g,  that  fits  in  the  groove  in  the  bar  b , and  a 
bracket  h with  vertical  adjustment  is  bolted  to  the  top  of  the 
bracket  and  has  a V-shaped  top  that  embraces  arid  supports 
the  shaft  of  the  engine  or  a mandrel  f\  when  the  mandrel  is 
properly  adjusted,  the  Babbitt  is  poured  in  the  two  boxes  i,  i. 

55.  A more  elaborate  fixture  for  holding  the  mandrel, 
and  one  that  is  self-centering,  is  shown  in  Fig.  11.  The 


I1  o 
1 1 
n 
1 1 


O 

b 

O 

o 

b 

O 

c 

> H) 

a 

TEf 

\A=p  b 

vdi 

Fig.  11. 

lower  guide  bars  on  the  engine  bed  a having  been  planed,  a 
fixture  shown  at  b is  placed  at  each  end  of  the  engine  guides 
and  these  support  a bar  c with  a casting  d on  the  end  to  hold 
the  babbitting  mandrel  e. 

Different  sized  boxes  may  be  babbitted  by  having  several 
mandrels  all  the  same  size  in  the  center  d , but  of  smaller 
diameter  in  the  journals  f,  f.  The  center  of  the  hole  in  d 
for  holding  the  mandrel  e can  be  bored,  if  desired,  -J-  inch  or 
so  higher  than  the  center  of  the  hole  for  the  bar  c.  This 
will  allow  for  the  spring  of  the  bar  c and  also  bring  the  cen- 
ter of  the  journals  a little  above  the  center  line  of  the  engine, 
so  that  the  first  wear  will  be  down  toward  the  center  line 


68 


SHOP  HINTS. 


24 


and  not  away  from  it.  Keys  may  be  fitted  in  the  shaft  c 
and  the  castings  b and  d to  level  the  mandrel  e,  or  the  keys 
may  be  omitted  and  the  mandrel  e leveled  by  a surface  gauge 
on  the  floor  plate  under  the  engine  bed,  or  a spirit  level  may 
be  used  on  the  mandrel  e.  The  rig  shown  in  Fig.  11  can  be 
made  to  serve  for  babbitting  two  sizes  of  engine  by  making 
the  casting  b with  two  sets  of  shoulders  g,  g and  h,  h to  fit 
the  guides  of  two  sizes  of  engine. 

5(4.  When  a large  number  of  engines  are  to  be  built, 
a babbitting  jig  may  be  made  for  each  size,  as  shown  in 
Fig.  12,  which  is  a single  casting  a with  a rib  b to  stiffen  it. 


The  casting  is  planed  under  the  lugs  c,  c to  fit  the  engine 
guides  and  bored  at  the  end  d so  as  to  receive  and  support 
the  babbitting  mandrel.  Many  other  forms  of  mandrels  may 
be  designed  to  meet  the  requirements  of  the  case  in  hand. 

57.  Rebabbitting  a Box. — In  case  a babbitted  box 
is  so  worn  down  as  to  require  renewal,  first  chip  out  the 
old  Babbitt  metal  and  then  proceed  to  rebabbitt  as  nearly 
in  the  way  described  for  a new  box  as  the  appliances  at 
hand  will  permit. 

58.  Babbitting  Journal  Brasses.  — Journal-box 
brasses  are  sometimes  lined  with  Babbitt  metal.  It  is  neces- 
sary to  tin  the  surface  of  the  brass  so  that  the  Babbitt  will 
adhere  to  it.  The  surface  must  first  be  made  bright  and 
clean  by  machining,  grinding,  or  pickling;  it  is  then  heated 
a little  above  the  melting  point  of  tin,  445°  F.,  moistened 
with  tinning  solution,  and  a stick  of  tin  rubbed  on  the  sur- 
face. The  tinning  solution  is  made  by  dissolving  zinc  in 


§24 


SHOP  HINTS. 


69 


muriatic  acid;  sometimes  sal  ammoniac  is  added.  Tinning 
salts  are  also  on  the  market.  After  the  surface  is  thoroughly 
tinned,  the  Babbitt  is  poured  in  the  usual  way,  but  in  this 
case  unites  with  the  tin  and  is  held  firmly  to  the  brass. 


59.  A special  mandrel  for  babbitting  brasses  is  shown 
in  Fig.  13.  The  mandrel  consists  of  a hollow  cast-iron  cylin- 
der a resting  on  a 
base  b bolted  to  a 
table  c.  The  cylin- 
der a is  turned  to  the 
proper  diameter  to  fit 
the  brasses  d,  and  has 
two  lugs  e , e for  the 
edges  of  the  brasses  to 
rest  against,  leaving  a 
space  f between  the 
mandrel  and  the  sur- 
face of  the  brass  that 
is  to  be  filled  with  Bab- 
bitt. The  brass  d 
stands  on  the  base  b 
and  is  held  against  the  lugs  e,  e of  the  mandrel  a by  means 
of  a curved  lever  g hinged  to  the  frame  at  h.  The  Babbitt 
is  poured  from  a dipper  into  the  space  f9  and  the  brass  is 
removed  as  soon  as  the  metal  sets.  The  cast-iron  mandrel  a 
is  cooled  by  means  of  a circulation  of  water  that  enters 
through  a pipe  i attached  to  the  center  at  the  bottom. 


Fig.  13. 


USEFUL  INFORMATION. 

Of).  Putting  in  Wood  Screws. — The  machinist  is 
sometimes  obliged  to  put  in  wood  screws.  These  can  be 
screwed  home  easier  if  they  are  rubbed  with,  or  stuck  into, 
a cake  of  tallow,  while  in  the  absence  of  tallow  any  heavy 
grease  or  oil  may  be  used.  Screws  that  are  thus  lubricated 
may  be  easily  taken  out  again.  Wood  screws  may  be  put 
into  the  hardest  wood  by  the  following  process:  A screw  of 


70 


SHOP  HINTS. 


§24 


the  size  to  be  used  is  filed  or  ground  to  the  form  of  a half- 
round  bit,  thus  making  a tap  of  it.  A hole,  equal  in  diam- 
eter to  the  size  of  the  screw  at  the  bottom  of  the  thread,  is 
drilled  or  bored  into  the  wood  and  the  half-round  tap  is 
screwed  in.  This  cuts  a good  thread  into  which  the  screw, 
which  should  be  well  greased,  may  be  easily  screwed. 

61.  Cutting  Soft  Rubber. — Soft  rubber  is  very  hard 
to  cut  smoothly,  even  when  the  knife  is  very  sharp.  It  can 
be  cut  quite  easily,  however,  if  the  knife,  which  must  be 
sharp,  is  dipped  frequently  into  water,  or  wet  with  saliva. 

62.  Working  Vulcanized  Rubber.  — Vulcanized 
rubber,  which  is  more  frequently  called  hard  rubber,  is  a 
material  that  is  hard  to  machine  smoothly  on  account  of 
the  fact  that  it  dulls  the  tool  very  rapidly.  The  tool  used 
for  turning  or  planing  it  may  be  a little  keener  than  that 
used  for  steel,  and  should  be  left  just  as  hard  as  fire  and 
water  can  make  it.  Hard  rubber  can  be  machined  to  the 
best  advantage  with  a diamond-tipped  tool.  Vulcanized 
rubber  will  take  a high  finish,  which  is  obtained  by  buffing 
it  on  an  ordinary  buffing  wheel. 

63.  Bluing  Iron  and  Steel. — Polished  work  made 
of  iron  or  steel  may  be  given  a beautiful  blue  color  by 
heating  it  in  hot  sand,  in  wood  ashes,  or  in  pulverized 
charcoal.  The  substance  in  which  the  article  is  to  be  blued 
may  be  put  into  an  iron  kettle  that  is  placed  over  a fire. 
The  substance  must  be  constantly  stirred  while  it  is  being 
heated  in  order  that  the  whole  of  it  may  be  brought  to  an 
even  temperature.  The  article  or  articles  to  be  blued  must 
be  absolutely  free  from  grease  if  an  even  color  is  desired ; 
they  may  be  placed  into  a wire  basket  or  may  be  suspended 
by  wires  and  then  immersed  in  the  heated  substance  until 
the  desired  color  is  obtained.  A light-blue  color  can  be 
obtained  by  heating  in  sand  or  wood  ashes,  but  a dark-blue 
color  requires  the  article  to  be  heated  in  pulverized  charcoal. 
The  brightness  of  the  color  depends  largely  on  the  finish; 
the  higher  the  polish  upon  the  work,  the  more  brilliant  the 
color  which  will  be  obtained.  The  substance  in  which  the 


24 


SHOP  HINTS. 


71 


heating  is  done  should  be  just  hot  enough  to  char  a dry  pine 
stick.  By  this  manner  of  bluing,  a piece  of  work  having 
thick  and  thin  parts  can  be  given  an  even  color  all  over. 

(->4.  Blacking  Iron  and  Steel. — Polished  articles  of 
iron  and  steel  can  be  given  a deep  lustrous  black  color  by 
immersing  them  into  a heated  mixture  composed  of  1 part 
of  black  oxide  of  manganese  and  10  parts  of  saltpeter,  by 
weight.  This  mixture  should  be  heated  in  an  iron  kettle 
until  it  is  hot  enough  to  char  a pine  stick.  The  articles  to 
be  blackened  must  be  scrupulously  clean;  the  excellence  of 
the  color  will  depend  on  the  degree  of  finish  of  the  work. 

When  bluing  or  blacking  articles  in  a heated  substance,  it 
must  be  remembered  that  the  articles  will  themselves  become 
heated,  and  that  if  they  are  hardened,  the  temper  will  be 
drawn. 

65.  Browning  Iron  and  Steel  Chemically. — Many 
articles  of  iron  and  steel  can  be  given  a color  varying  from 
a light  brown  to  a deep  black  by  a chemical  treatment.  For 
this  purpose  a solution  composed  of  1 part  of  corrosive  sub- 
limate dissolved  in  a mixture  of  16  parts  of  sweet  spirits  of 
niter  and  16  parts  of  alcohol,  by  weight,  is  used.  The  article 
to  be  browned  is  cleaned  thoroughly,  so  as  to  be  free  from 
grease,  and  is  then  washed  with  wet  lime,  and  finally 
rubbed  down  with  dry  lime,  in  order  to  eliminate  all  traces 
of  grease,  as  the  success  of  the  treatment  depends  on  it. 
Care  must  also  be  taken  not  to  touch  the  article  with  the 
fingers  after  it  has  been  cleaned,  by  fitting  wooden  handles 
to  it  by  which  it  can  be  held.  The  article  having  been 
cleaned,  the  browning  solution  is  applied  with  a sponge  and 
the  article  is  put  in  a dark,  dry  place  until  a dry  rust  has 
formed  on  it.  This  will  take  from  8 to  48  hours,  depending 
on  the  condition  of  the  weather  and  the  hardness  of  the 
material.  When  the  rust  has  become  dry  enough  to  fly 
when  a file  card  is  applied  to  it,  the  article  is  carded  off  with 
a card  that  must  be  absolutely  free  from  grease;  it  will  now 
be  found  to  have  a light-yellow  color.  Another  coat  of  the 
browning  solution  is  now  applied  and  after  the  dry  rust  has 


CAPSCREW  HEADS 


72 


SHOP  HINTS. 


§24 


*The  angle  of  the  conical  head  of  the  flat  or  countersunk  head  is  72°.  f No.  4 wire. 


SHOP  HINTS. 


73 


§ 24 

formed,  the  article  is  again  carded  off,  when  it  will  be  found 
to  have  a dark-yellow  color.  The  next  repetition  of  the 
process  will  give  it  a light-brown  color,  then  a dark-brown, 
and  finally,  a deep-brown.  The  deep-brown  color  is  changed 
to  a black  color  by  immersing  the  article  in  boiling  water 
for  a few  minutes.  After  the  article  has  dried,  and  while 
still  hot,  it  should  be  given  a coat  of  oil  and  be  allowed 
to  cool  slowly. 

A more  lasting  black  color  can  be  obtained  if  the  article 
is  put  into  an  oven  that  is  heated  by  steam  to  a temperature 
of  300°  F.,  and  keeping  it  there  for  about  8 hours.  Instead 
of  the  file  card,  a rotary  steel-wire  brush  may  be  used  to 
advantage  when  much  browning  is  to  be  done.  The  barrels 
of  firearms  are  browned  by  the  process  just  described,  or  by 
modifications  of  it. 

Capscrews. — It  is  frequently  desirable  to  know 
the  diameter  and  the  length  of  the  head  of  a capscrew  of 
given  form.  Table  VI  gives  these  dimensions  for  five 
different  forms  of  capscrew  heads,  for  screws  ranging  from 

inch  to  inches  in  diameter. 


C.  S.  III.  28 


TOOLMAKING. 

(PART  1.) 


GENERAL  TOOL-ROOM  WORK. 


INTRODUCTION. 

1.  Definition. — Toolmaking  may,  in  general,  be 
defined  as  the  making  of  tools.  A tool  in  its  broadest 
sense  may  be  any  device,  instrument,  appliance,  machine, 
or  apparatus  that  is  intended  to  perform  some  essential  func- 
tion in  the  production  or  transformation  of  raw  material 
into  a finished  product  or  that  aids  in  the  performance  of 
some  function  required  for  the  change. 

Custom,  however,  has  narrowed  this  definition  until  the 
term  toolmaking  now  comprises  only  the  production  of  tools 
by  the  aid  of  which  the  integral  parts  of  devices,  instru- 
ments, appliances,  machines,  or  apparatus  can  be  formed 
through  cutting,  drawing,  compressing,  or  abrading  opera- 
tions performed  on  bodies  susceptible  to  these  operations. 
The  most  important  subdivision  of  toolmaking  relates  to 
the  production  of  tools  for  the  working  of  metals,  and  is  the 
one  that  will  be  treated  of  here. 


METHOD  OF  PROCEDURE. 

2.  There  are  several  stages  in  the  production  of  tools; 
it  is  rather  difficult,  however,  to  draw  a distinct  line  of 
demarkation  between  the  ending  of  one  stage  and  the 
beginning  of  the  other,  since  they  frequently  blend  more 
or  less  together,  according  to  the  circumstances  of  each 

§ 25 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


TOOLMAKING. 


25 


individual  case.  Generally  speaking,  these  stages  are  as 
follows:  conception  ; commercial  consideration  ; design  ; and, 
finally,  construction.  The  stages  follow  in  the  order  named. 

3.  Conception  of  tlie  Possibility  of  Improve- 
ment.— This  may  be  considered  as  the  foundation  of  prog- 
ress. Ability  to  conceive  possibilities  requires  not  only 
intimate  knowledge  of  every  stage  of  the  particular  process 
or  operation  under  consideration,  but  also  full  knowledge  of 
the  good  points,  defects,  capabilities,  and  limitations  of  the 
tools  used  for  this  process  or  operation. 

4.  Study  of  tlie  Commercial  Considerations. — 

Will  the  improvement  pay  ? This  question  must  be  asked 
in  each  and  every  case,  and  must  have  been  answered  in  the 
affirmative  before  any  further  step  is  taken.  Naturally, 
each  case  must  be  investigated  by  itself  and  decided  upon 
its  own  merits.  First  of  all,  the  probable  cost  of  improve- 
ment must  be  estimated;  the  saving  that  the  improvement 
will  effect  must  then  be  carefully  investigated.  Finally,  it 
must  be  determined  if  the  ratio  that  the  saving  bears  to  the 
investment  required  to  effect  it  is  sufficient  to  warrant  the 
expenditure.  It  is  always  to  be  remembered  that  the  pri- 
mary object  of  tool  improvement  is  the  lessening  of  the  cost 
of  production,  or  the  analogous  object  of  raising  the  quality 
of  the  output  without  increasing  the  selling  price. 

5.  Design. — Since  the  cost  of  a tool  depends  largely  on 
its  design,  and  since  the  latter  also  directly  determines  its 
ultimate  value,  it  will  be  apparent  that  the  design  is  a very 
important  matter.  It  must  always  be  remembered  that 
there  are  usually  quite  a number  of  different  ways  in  which 
an  object  can  be  accomplished;  then,  in  order  that  the  first 
cost  of  a tool  shall  be  within  reasonable  limits,  it  is  neces- 
sary to  carefully  study  the  facilities  at  command.  This  con- 
sideration shows  the  importance  of  a thorough  knowledge  of 
tool-room  operations,  appliances,  and  special  processes. 
For  this  reason,  in  the  majority  of  manufacturing  establish- 
ments, the  design  of  special  tools  is  left  entirely  to  the  tool- 
maker  or  to  special  designers. 


TOOLMAKING. 


3 


§ 25 

When  designing  a tool,  various  ways  of  accomplishing  the 
object  sought  will  present  themselves  successively;  unless 
special  considerations  prevent  it,  the  design  that  will  accom- 
plish the  object  in  the  most  direct  manner  is  the  one  to  be 
chosen.  A good  tool  designer  will  never  introduce  compli- 
cated mechanical  movements  or  such  special  modifications 
of  relatively  simple  ones  as  are  not  only  expensive  to  pro- 
duce but  difficult  to  keep  in  proper  alinement.  Simplicity, 
accessibility,  compactness,  rigidity,  durability,  and  handi- 
ness are  the  prime  factors  requisite  in  a successful  tool, 
whether  it  be  a boring  machine  for  boring  the  largest  sizes 
of  steam-engine  cylinders,  or  a box  tool  for  a small  automatic 
screw  machine. 

6.  Construction. — In  the  construction  of  tools,  the 
toolmaker  is  very  frequently  called  on  to  solve  problems 
that,  while  not  essentially  different  from  those  of  the  ma- 
chinist, still  require  entirely  different  methocls  of  procedure 
to  accomplish  the  object  sought.  Thus,  the  problem  of 
locating  and  drilling  a couple  of  bolt  holes  3 inches  apart, 
when  the  bolts  have  a clearance  of  inch  or  more,  is  solved 
in  an  entirely  different  manner  from  that  of  producing  two 
holes  with  their  axes  parallel  and  in  the  same  plane,  and 
3 inches  apart,  within  a limit  of  variation  not  to  exceed 
it innr  inch.  In  the  first  case,  the  combination  of  a drill  press, 
center  punch,  hammer,  2-foot  rule,  a drill,  and  a laborer 
will  usually  be  sufficient;  in  the  second  case,  an  accurate 
lathe  kept  in  the  best  of  condition,  fine  measuring  tools, 
standard  test  gauges,  an  extremely  sensitive  indicator,  and 
other  special  appliances  used  by  a highly  skilled  toolmaker, 
will  be  needed  to  locate  the  holes  within  the  given  limit  of 
variation. 

In  the  construction  of  a tool,  the  purpose  of  every  part  of 
it  must  be  taken  into  consideration  in  order  to  prevent  undue 
accuracy  and  unnecessary  expense  consequent  thereto.  It 
is  a mistake  to  accurately  machine,  scrape,  and  finish  parts 
that  may  be  said  to  “ fit  a hole  in  the  air.”  The  time  needed 
for  this  can  be  spent  more  profitably  on  those  parts  that 


4 


TOOLMAKING. 


§25 


accomplish  a useful  purpose;  likewise,  it  is  unnecessary  and  a 
direct  waste  of  time  to  go  to  the  utmost  refinement  of  meas- 
urement in  a gauge  that  may  be  “plenty  good  enough  ” if 
accurate  within  fa  inch — as  a gauge  for  the  blacksmith,  for 
instance.  Before  constructing  a tool,  the  purpose  and  the 
accuracy  required  for  each  integral  part  of  it  should  be 
studied;  the  operations  necessary  to  produce  it  can  then  be 
regulated  accordingly. 

7.  The  design  and  construction  of  a tool  are  intimately 
correlated,  as  becomes  painfully  apparent  when  special  meth- 
ods needed  for  its  construction  have  not  been  taken  into  ac- 
count and  it  becomes  necessary  to  devise  expensive  makeshifts 
in  order  that  the  whole  work  previously  done  on  the  tool  may 
not  be  lost.  For  this  reason,  no  matter  by  whom  the  tool  has 
been  designed,  it  is  good  practice  to  go  over  the  whole  design 
and  see  if  every  operation  required  in  the  production  of  the 
tool  can  be  actually  performed  with  the  facilities  at  hand.  If 
not,  and  when  circumstances  permit  it,  the  design  should  be 
changed;  provided,  of  course,  that  the  change  will  not 
affect  the  efficiency. 


DIMENSIONING  DRAWINGS. 

8.  In  dimensioning  a drawing,  it  should  always  be  the 
aim  to  give  all  dimensions  with  special  reference  to  the 
manner  in  which  the  tool  must  be  constructed.  If  the  tool- 
maker  will  have  to  work  from  some  certain  surface  in  order 
to  lay  out  the  different  parts  of  the  tool,  and  will  have  to 
make  all  his  measurements  from  it,  let  all  dimensions  on 
the  drawing  or  sketch  read  from  that  surface.  If  this  plan 
is  followed,  a great  deal  of  needless  work  is  obviated.  When 
giving  the  distance  between  holes  that  have  to  be  accurately 
located  in  reference  to  each  other  and  in  reference  to  some 
fixed  point  of  the  tool,  put  in  all  the  dimensions  that  the 
toolmaker  needs  to  thus  locate  them ; this  is  better  than 
expecting  him  to  make  these  calculations  himself. 


§25 


TOOLMAKING. 


5 


A case  in  point  is  shown  in  Fig.  1.  In  view  (a),  part  of  a 
jig  is  shown  in  which  the  three  holes  are  to  be  located  with 
reference  to  one  another  and  to  the 
finished  surfaces  a and  b,  as  shown 
by  the  dimensions.  The  dimen- 
sions given  would  be  sufficient  for 
work  not  requiring  any  great  de- 
gree of  accuracy,  say  for  ordinary 
machinist’s  work.  With  these  di- 
mensions, the  aid  of  a surface 
gauge,  a surface  plate,  an  angle 
block,  and  by  extremely  careful 
work,  the  centers  may  be  laid  out 
within  a limit  of  error  of  1 030  0 inch, 
and  an  expert  may  even  bore  the 
holes  within  that  limit  of  variation. 

But  suppose  that  a greater  degree 
of  accuracy  is  required;  assume 
that  the  limit  of  variation  is  not 
to  exceed  one-half  of  yoVo*  ^ch- 
in order  to  obtain  this  degree  of 
accuracy,  which  must  not  be  imagined  to  be  anything 
extraordinary,  the  toolmaker  must  substitute  contact 
measurements  for  measurements  taken  from  a scale  and 
then  transferred  by  scribed  lines  to  the  work. . In  order  to 
make  these  contact  measurements,  the  toolmaker  needs  the 
dimensions  marked  x,  y,  and  z in  Fig.  1 (b) ; if  these  are 
not  given,  he  cannot  conclude  the  work  until  they  are 
supplied. 

9.  Referring  again  to  Fig.  1 (a),  it  will  be  noticed  that 
the  dimensions  locating  the  holes  with  reference  to  one 
another  and  to  the  surfaces  a and  b are  given  in  decimal 
parts  of  an  inch,  and  the  other  dimensions  in  common  frac- 
tions. This  is  done  in  accordance  with  a method  of  dimen- 
sioning that,  while  not  universal,  is  well  deserving  of  wider 
application.  It  simply  signifies  that  all  dimensions  given 
decimally  are  accurate  dimensions,  and  that  the  parts  are  to 


(a) 


G 


TOOLMAKING. 


§ 25 

be  located  or  made  to  those  dimensions  as  closely  as  can  be 
measured  with  a micrometer,  vernier  calipers,  or  similar 
measuring  instrument  decimally  graduated.  On  the  other 
hand,  for  those  dimensions  that  are  expressed  in  common 
fractions,  no  great  accuracy  in  machining  or  fitting  is 
required.  If  this  system  of  dimensioning  is  adopted,  it 
usually  results  in  the  reduction  of  needless  accuracy,  which, 
in  turn,  means  a decided  saving  in  the  labor  cost. 

On  good  work  it  is  often  advisable  to  specify  on  the  draw- 
ing the  limit  of  variation  permissible;  this  prevents  choice 
of  methods  entailing  a vast  amount  of  work  when  less  elab- 
orate methods  will  produce  a job  that  is  “good  enough  for 
the  purpose.” 


READING  DECIMALS. 

lO.  Since,  with  very  rare  exceptions,  the  measuring 
instruments  of  the  toolmaker  are  graduated  to  read  to  the 
one-thousandth  part  of  an  inch,  and  some  to  the  one  ten- 
thousandth  part  of  an  inch,  dimensions  on  drawings  for  tool 
work  are  in  many  cases  given  decimally.  Trouble  is  expe- 
rienced occasionally  in  reading  them  correctly,  hence  a 
short  explanation  of  how  to  read  decimals  is  here  given. 
The  method  given,  while  differing  from  that  laid  down  in 
works  on  arithmetic,  is  in  common  use  in  shops,  and  is 
especially  adapted  to  the  needs  of  the  toolmaker  on  account 
of  the  graduations  of  his  measuring  instruments  reading 
directly  to  thousandths  of  an  inch.  As  decimals  containing 
more  than  four  figures  are  very  rarely  met  with  in  tool 
work,  their  reading  will  not  be  considered  here. 

Rule. — Read  the  first  three  figures  to  the  right  of  the  deci- 
mal point  .as  a common  fraction  having  one  thousand  for  its 
denominator , and  read  the  fourth  figure  as  a fraction  having 
ten  for  its  denominator  and  one  one-thousandth  of  an  inch  as 
a unit. 

Figures  to  the  left  of  the  decimal  point  are  whole  num- 
bers and  are  to  be  read  as  such.  Commence  reading  the 


TOOLMAKING. 


§ 25 


7 


decimal  at  the  first  figure  greater  than  zero,  reading  from 
left  to  right.  For  example,  1.0567*  would  be  read,  one  and 
fifty-six  one-thousandths  and  seven-tenths  of  a thousandth 
of  an  inch ; .0005''  may  be  read,  five-tenths  of  a thousandth  of 
an  inch;  .072"  would  be,  seventy-two  one-thousandths  of  an 
inch.  When  there  are  less  than  three  figures  to  the  right 
of  the  decimal  point,  annex  enough  ciphers  mentally  to 
make  three  figures.  Thus,  .07"  would  be  read  as  though  it 
were  written  .070"  and  may  be  expressed  as  seventy  one- 
thousandths  of  an  inch,  and  .4"  would  be  read  as  though  it 
were  written  .400",  i.  e.,  four  hundred  one-thousandths  of 
an  inch. 

Suppose  a micrometer  graduated  to  read  to  ten-thou- 
sandths of  an  inch  is  to  be  set  to  read  .7653  inch.  Then, 
since  on  all  portable  micrometers  the  one-thousandth  of  an 
inch  graduations  are  independent  of  the  vernier  by  which 
the  tenth  part  of  a one-thousandth  is  obtained,  the  microm- 
eter would  be  set  first  to  seven  hundred  sixty-five  one- 
thousandths,  and  then,  by  the  aid  of  the  vernier,  set  ahead 
three-tenths  of  one-thousandth  of  an  inch.  By  accustom- 
ing himself  to  read  decimals  in  this  manner,  a person  is 
less  liable  to  make  an  error  in  setting  or  in  reading  the 
micrometer. 


WORK  OF  THE  TOOLMAKER. 

11.  In  its  broadest  sense,  the  work  of  the  toolmaker 
comprises  the  design  and  construction  of  machine  tools, 
such  as  lathes,  planers,  shapers,  etc.,  in  addition  to  that  of 
the  small  general  tools,  such  as  taps,  dies,  reamers,  milling 
cutters,  and  the  special  tools,  such  as  jigs,  gauges,  and 
similar  implements  used  in  the  production  of  duplicate 
work.  It  being  the  tendency  to  specialize  in  every  direc- 
tion of  machine-shop  work,  the  journeyman  toolmaker  today 
does  not  generally  build  the  machine  tools  himself,  but, 
instead,  produces  the  tools  and  special  appliances  for  the 
construction  of  the  machine  tools  in  an  economical  manner. 

The  making  of  taps,  dies,  reamers,  milling  cutters,  and 


8 


TOOLMAKING. 


25 


similar  cutting1  tools  forms,  in  most  shops,  but  a relatively 
small  part  of  the  toolmaker’s  work,  since  there  are  many 
concerns  making  a specialty  of  this  work.  In  consequence 
thereof,  all  such  tools  can  be  bought  of  the  makers  for  a 
small  fraction  of  what  their  cost  would  be  if  made  singly  and 
with  the  facilities  usually  found  in  tool  rooms.  Many  of 
these  tools  thus  bought  are  really  superior  to  home-made 
tools,  simply  on  account  of  the  makers  having  the  proper 
facilities. 

As  far  as  cutting  tools  are  concerned,  the  work  of  the 
individual  toolmaker  is  confined,  except  in  relatively  rare 
instances,  to  the  making  of  special  cutting  tools  differing  in 
one  or  more  dimensions  or  in  design  from  the  standard  sizes 
in  which  the  makers  supply  them.  The  production  of  the 
special  tools  used  where  articles  are  manufactured  in  quan- 
tities under  the  interchangeable  system,  and  such  special 
tools  as  tend  to  cheapen  the  cost  of  manufacture  where 
machinery  is  not  built  in  large  quantities,  form,  in  general, 
by  far  the  greater  part  of  the  toolmaker’s  work. 


MEASUREMENTS. 

12.  Classification  of  Measurements. — The  meas- 
urements to  be  made  in  tool  construction  may  be  divided 
into  two  general  classes:  (1)  Approximate  measurements; 
(2)  precise  measurements.  The  adoption  of  one  or  the 
other  class  of  measurement  depends  on  the  accuracy 
required.  In  most  cases,  both  classes  of  measurement  are 
used  on  a job,  since  a tool  is  rarely  of  such  shape  as  to 
require  measurements  of  precision  for  each  and  every  part 
of  it. 


13.  Approximate  measurements  are  those  made 
with  the  aid  of  an  ordinary  graduated  steel  scale  and  a 
caliper,  dividers,  scribing  block,  surface  gauge,  etc.,  or 
measurements  that  may  be  classified  as  direct  visual  meas- 
urements. While  an  expert  using  the  greatest  care  and 


TOOLMAKING. 


0 


§ 25 

working  with  a magnifying  glass  can  set  calipers  by  a steel 
scale  within  a limit  of  variation  of  .001  inch  of  the  true 
size,  there  are  rather  few  people  that  can  do  so.  Generally 
speaking,  the  limit  of  variation,  that  is,  the  degree  of  accu- 
racy attainable,  may  be  placed  at  .002  inch;  it  requires 
quite  close  work  to  attain  this  accuracy. 

14.  Precise  measurements  depend  primarily  on 
gauges  of  various  kinds  that  represent  commercially  accu- 
rate subdivisions  of  the  standard  yard.  These  gauges, 
among  which  may  be  mentioned  the  standard  end-measure 
pieces  made  by  Pratt  & Whitney,  and  the  reference  disks 
made  by  Brown  & Sharpe,  are  carefully  ground  and  lapped 
to  a size  not  Varying  more  than  inch  from  the  true 

size.  Gauges  of  this  degree  of  accuracy  are  naturally  quite 
expensive,  and  hence  are  not  intended  for  use  in  the  machine 
shop,  but  rather  for  the  testing  of  micrometers,  vernier 
calipers,  and  similar  shop-measuring  instruments.  The 
precise  measurements  that  the  toolmaker  is  usually  called 
on  to  make  depend  for  their  precision  on  his  sense  of 
touch,  they  being  chiefly  measurements  of  contact.  As  a 
matter  of  course,  it  is  here  assumed  that  the  measuring 
instrument  used — as  a micrometer,  for  instance — is  com- 
mercially correct. 

With  an  accurate  instrument  and  a finely  developed  sense 
of  touch,  a surprising  degree  of  accuracy  can  be  obtained  by 
direct-contact  measurement.  Instances  are  numerous  where 
toolmakers  have  finished  work  that,  upon  testing  by  more 
refined  methods,  was  shown  to  be  accurate  within  -g-o^or  inch. 
To  attain  this  degree  of  accuracy,  a long  training  is  required  ; 
however,  very  little  work  that  the  toolmaker  is  called  on 
to  do  will  need  to  be  within  this  limit.  To  attain  accuracy 
within  a limit  of  variation  of  .0001  inch  is  possible  for 
almost  any  one  that  possesses  a sensitive  touch.  It  may 
sound  like  a very  small  amount,  but  its  magnitude  will  be 
realized  very  forcibly  when  a hardened,  ground,  and  lapped 
cylindrical  plug  is  placed  between  the  anvils  of  a microm- 
eter set  to  just  touch  the  plug.  Let  the  micrometer  be 


10 


TOOLMAKING. 


§ 25 

screwed  up  .0001  inch  and  let  the  difference  in  the  force 
required  to  push  the  plug  through  the  opening  be  noted. 
The  difference  will  prove  a surprise  to  any  one  that  has 
never  felt  this  demonstration  of  the  magnitude  of  the  tenth 
part  of  one-thousandth  of  an  inch.  While  granting  that  an 
expert  may  attain  a greater  accuracy,  generally  speaking, 
the  limit  of  accuracy  of  ordinary  contact  measurements  may 
be  placed  at  that  figure. 

1 5.  Accumulation  of  Errors.  — It  must  not  be 
inferred,  however,  that  all  work  can  be  done  or  is  done 
within  this  limit  of  variation  ; while  it  is  possible  to  attain  this 
accuracy  for  one  contact  measurement,  it  is  unreasonable  to 
expect  to  get  it  when  a number  of  successive  contact  meas- 
urements have  to  be  made  in  order  to  obtain  a precise  over- 
all dimension.  Naturally,  the  total  error  will  very  likely  be 
more  than  the  error  of  each  individual  measurement. 

A case  illustrating  this  is  shown  in  Fig.  2.  The  problem 
given  is  one  that  frequently  arises  in  one  form  or  another. 


In  this  case,  a row  of  six  holes  is  to  be  bored  in  some  part  of 
a jig;  the  holes  are  to  be  in  a straight  line,  equidistant,  and 
1 inch  apart.  It  is  required  that  the  holes  be  bored  with  the 
greatest  possible  degree  of  accuracy  attainable  with  the 
measuring  instruments  at  hand,  which  are  limited  to  a 1-inch 
micrometer.  Under  the  circumstances,  some  toolmakers 
would  locate  the  centers  of  the  holes  by  temporarily  attach- 
ing small  annular  circular  steel  disks  of  known  diameter  to 
the  work  by  fillister-headed  screws  and  placing  them  the  re- 
quired distance  apart  by  the  aid  of  a temporary  gauge  filed 


TOOLMAKING. 


11 


§25 

up  to  a length  equal  to  the  center  distance  of  two  adjacent 
holes  diminished  by  the  sum  of  the  radii  of  the  two  adjacent 
disks.  If  all  disks  are  alike,  the  same  temporary  gauge  will 
answer  for  each  division.  The  disks  are  placed  in  line  by 
being  brought  up  against  a true  straightedge.  The  work  is 
then  placed  on  the  face  plate  of  the  lathe  and  trued  up  until 
one  disk  runs  true;  the  disk  is  now  removed  and  the  hole 
bored.  This  operation  is  repeated  until  all  the  holes  have 
been  bored.  Now,  while  each  hole  may  have  been  located 
originally  within  say  yowo  ^nc^’  the  errors  °f  each  meas- 
urement may  have  accumulated  until  the  center-to-center 
distance  between  the  end  holes  may  vary  an  amount  consid- 
erably in  excess  of  the  limit  of  variation  of  a single  contact 
measurement. 

16.  In  a job  of  the  kind  here  shown,  the  errors  that 
prevent  absolute  accuracy  are  as  follows: 

1.  The  error  of  the  measuring  instrument.  This,  with  an 
instrument  purchased  of  a reliable  maker,  is  usually  exceed- 
ingly small. 

2.  Error  in  measuring  the  size  of  the  disks.  This  should 
not  exceed  .0001  inch. 

3.  Error  in  making  the  temporary  gauge.  This  need  not 
be  more  than  the  previous  error. 

4.  Error  in  placing  the  disks  equidistant  and  at  the  re- 
quired distance.  Its  magnitude  will  be  a combination  of 
errors  2,  3,  and  4.  These  errors  may  accumulate  or  neu- 
tralize, partially  or  entirely. 

5.  Error  in  chucking  the  disk  to  run  true.  This  error 
need  not  exceed  .0001  inch  if  a sensitive  indicator  is  used. 

6.  Error  in  boring.  Its  magnitude  depends  on  the  skill  of 
the  toolmaker;  it  may  be  infinitesimal  or  quite  appreciable. 

Examining  into  these  errors  and  knowing  that  some  of 
them  cannot  be  obviated  entirely,  it  is  seen  that  the  best 
that  can  be  done  is  to  reduce  each  individual  error  to 


TOOLMAKING. 


§25 


12 

the  lowest  possible  limit.  The  better  the  sense  of  touch  is 
trained  and  the  more  skill  is  used,  the  closer  a final  result 
may  be  attained. 

1 7.  Reduction  of  Accumulating  Errors. — We  will 

now  investigate  the  elimination  of  errors  for  this  particular 
case.  Suppose  that  a 2-inch  micrometer  is  at  the  disposal 
of  the  toolmaker.  Then  error  3 can  be  eliminated  entirely, 
since  the  micrometer  can  be  used  directly  over  any  two 
adjacent  disks.  Error  4 will  also  be  reduced,  since  there  is 
one  measurement  less  to  be  made  for  the  location  of  any 
two  adjacent  disks;  that  is,  there  are  now  three  contact 
measurements  instead  of  four.  Error  2 can  be  diminished 
when  the  disks  are  exactly  alike  by  placing  three  or  four  of 
them  on  a surface  plate,  pushing  them  all  in  contact  with 
a straightedge  and  one  another,  and  then  measuring  their 
combined  size,  finally  dividing  the  measurement  by  the 
number  of  disks.  Error  1 cannot  readily  be  eliminated  by 
any  means  at  the  command  of  the  toolmaker.  Errors  5 
and  6 can  be  minimized  by  careful  work. 

From  the  preceding  discussion,  it  is  seen  that  a careful 
study  of  the  way  in  which  the  measurements  can  be  made  is 
advisable  in  order  to  secure  accuracy.  In  general,  it  may 
be  stated  that,  in  order  to  secure  the  greatest  accuracy 
where  a number  of  successive  contact  measurements  are 
necessary,  the  number  of  the  measurements  should  be 
reduced  to  the  smallest  number  feasible  with  the  measuring 
instruments  at  disposal.  When  a number  of  successive 
measurements  are  needed  for  intermediate  parts  and  the 
object  sought  is  accuracy  of  the  combined  length  of  these 
intermediate  parts,  in  addition  to  their  own  accurate  location, 
make,  first  of  all,  the  longest  measurement  circumstances 
permit,  and  from  it  obtain  the  subdivisions.  This  applies 
not  only  to  precise  measurements,  but  to  approximate  meas- 
urements as  well.  For  illustration,  assume  that,  in  the  job 
shown  in  Fig.  2,  the  distance  between  the  end  holes  is  re- 
quired to  be  as  precise  as  it  can  be  made.  Then,  facilities 
permitting,  the  two  disks  locating  them  should  be  adjusted 


§25 


TOOLMAKING. 


13 


first  of  all,  and  the  intermediate  disks  from  these  in  turn. 
The  following  may  be  laid  down  as  a general  rule: 

Rule. — Where  several  methods  of  measurement  are  fea- 
sible, the  method  that  involves  the  fewest  and  most  direct 
measurements  should  always  be  chosen. 

18.  Considering  the  different  methods  of  measure- 
ment that  are  feasible,  it  will  be  seen  upon  reflection  that 
no  rules  can  be  given.  The  toolmaker  must  consider  the 
means  of  measurement  at  hand  and  the  nature  of  the  job; 
he  must  then  use  his  ingenuity  and  be  guided  by  his  prac- 
tical experience. 

19.  For  measurements  that  have  to  be  made  within  a 
smaller  limit  of  variation  than  is  attainable  by  direct-contact 
measurements,  special  forms  of  measuring  instruments  based 
on  the  principle  of  the  micrometer  are  used.  In  these 
machines,  special  devices  show  the  degree  of  contact  of  the 
measuring  surfaces  with  the  work.  They  are  to  be  found 
in  a few  of  the  leading  shops  where  accurate  work  is  done, 
being  intended  for  measurements  within  a limit  of  variation 
of  g0  loo  inch.  They  are  used  rarely  for  work  other  than 
making  standard  gauges  intended  for  testing  the  ordinary 
measuring  instruments.  For  measurements  closer  than  the 
above,  a machine  known  asa  “ comparator”  is  used.  Since 
it  can  scarcely  be  considered  as  a measuring  instrument 
suitable  for  tool-room  work,  it  will  not  be  described  here. 


LIMITATIONS  OF  TOOLMAIvING* 

20 .  The  limitations  of  toolmaking  are  twofold ; they  are 
limitations  of  accuracy  and  limitations  of  com- 
merce. The  first  depend  ultimately  on  the  degree  of  skill, 
knowledge,  and  ingenuity  of  the  individual  and  the  mechan- 
ical resources  at  disposal.  In  many  cases,  a sharply  defined 
limit  is  set  by  restriction  as  to  cost.  The  second  depend  on 
the  conditions  of  each  particular  case;  theoretically,  they 


14 


TOOLMAKING. 


§ 25 


may  be  said  to  have  been  reached  when  further  toolmaking 
fails  to  reduce  the  cost  of  production  or  to  improve  the 
quality.  As  a general  rule,  the  commercial  limitations  are 
reached  in  practice  when  the  cost  of  production  has  been 
reduced  below  that  of  competitors.  At  this  period,  in  most 
cases,  a halt  is  called  to  the  devising  of  new  tools  or  the 
improving  of  old  ones  until  further  advance  is  made  neces- 
sary by  competitors  lowering  the  selling  price  or  bettering 
the  quality  of  the  product. 


SPECIAL  TOOLS  USED  IN  TOOLMAKING. 

21.  In  addition  to  the  ordinary  measuring  instruments 
and  similar  devices  used  by  the  machinist,  the  toolmaker 
needs  an  indicator  for  showing  the  truth  of  cylindrical 
work,  and  also  a center  indicator.  There  is  quite  a variety 
of  other  tools  of  great  use  to  the  toolmaker,  but  since  these 
are  fully  described  in  the  catalogues  of  concerns  making  a 
specialty  of  measuring  instruments,  no  space  will  be  given 
to  them  here. 

The  lathe  indicator  and  center  indicator  have  been  com- 
paratively unknown  and  have  heretofore  been  made  by  the 
toolmaker  himself;  as  a consequence  there  is  a great  variety 
of  designs.  The  two  instruments  shown  in  Figs.  3 and  5 
and  the  holder  for  them  shown  in  Fig.  6 were  designed  by 
the  writer  and  have  been  used  by  him  constantly  for  fine 
work.  Their  construction  is  not  covered  by  patents.  Sev- 
eral firms  are  now  making  good  indicators. 

22.  Construction  of  a Lathe  Indicator.  — The 

lathe  indicator  is  shown  in  Fig.  3,  the  illustration  being  full 
size.  The  purpose  of  the  indicator  is  to  magnify  any  untruth 
of  the  work  in  order  to  make  the  error  more  visible ; the  most 
obvious  and  direct  method  is  to  use  a lever  with  a long  and 
a short  arm.  The  short  arm  bears  against  the  work.  When 
the  latter  is  revolved  in  the  lathe,  any  error,  due  either  to 
the  work  not  being  round  or  to  its  not  being  set  centrally, 


§25 


TOOLMAKING. 


15 


causes  the  end  of  the  long  arm  to  describe  an  arc,  the  length 
of  which  is  directly  proportional  to  the  ratio  between  the 
lengths  of  the  two  arms.  In  other  words,  the  longer  the 
long  arm  is  made  in  proportion  to  the  length  of  the  short 
arm,  the  more  sensitive  the  indicator  will  be.  In  practice, 
it  is  rarely  necessary  or  advisable  to  make  the  ratio  more 
than  1 to  50;  with  this  ratio,  an  error  in  the  work  amounting 
to  only  .0001  inch  will  cause  a movement  of  the  long  arm 


r,  — j~ 

oil  |!  b i)  i 

Syirr1 — r_— ...  .jvn- 

'l 

*= a 

1 

6 (b) 

— 

Fig.  3. 


through  an  arc  fifty  times  as  long,  or  .005  inch  in  length. 
This  is  an  amount  that  can  plainly  be  seen  with  the  naked 
eye.  If  the  indicator  is  made  more  sensitive  than  this,  it  is 
too  liable  to  be  affected  by  the  vibrations  of  the  floor  and 
machinery  that  exist  to  a greater  or  less  degree  in  all  shops. 
For  special  work  requiring  the  greatest  of  accuracy,  an  indi- 
cator may  be  constructed  with  a greater  degree  of  sensitive- 
ness than  that  here  recommended  as  the  limit  for  general 


C.  S'.  III.— 29 


16 


TOOLMAKING. 


25 


work;  in  that  case,  it  must  be  used  in  a place  free  from 
vibrations. 

23.  Referring  to  Fig.  3,  views  ( a ) and  (b)  are,  respect- 
ively, a side  elevation  and  a plan  view  of  the  indicator.  It 
consists  essentially  of  four  parts.  These  are  the  body  the 
lever  b , the  feeler  c , and  the  spring^.  For  convenience,  the 
lever  is  divided  into  two  parts  b and  b' . They  are  so  joined 
that  b\  which  forms  part  of  the  long  arm  of  the  lever,  can 
be  swiveled  to  any  convenient  position  within  range.  By 
means  of  the  locknut  e,  the  two  parts  may  be  locked  together 
after  adjustment.  The  division  of  the  lever  into  two  sep- 
arate parts  also  allows  the  degree  of  sensitiveness  to  be 
increased  or  decreased  by  the  substitution  of  different  arms. 
The  end  carrying  the  feeler  is  hardened;  the  hole  that 
receives  it  is  lapped  true  and  smooth.  The  feeler  itself  is 
hardened,  ground,  and  lapped  so  as  to  be  a good  sliding 
fit  in  the  hole.  Both  of  its  ends  are  hemispherical;  the 
upper  end  is  enlarged  to  form  a stop.  The  chief  peculiarity 
of  the  lever  is  the  manner  in  which  it  is  fulcrumed,  the  ful- 
crum being  so  designed  that  not  only  is  all  wear  taken  up 
automatically,  but  also  the  possibility  of  any  lost  motion  at 
the  fulcrum  is  done  away  with.  This  is  done  without  the 
introduction  of  any  complicated  device. 

Referring  to  view  (r),  which  is  a detail  drawing  of  the 
main  part  of  the  lever,  it  is  seen  that  the  fulcrum  pin  f is 
held  by  its  ends  in  the  two  wings  that  straddle  the  end  of 
the  body  a.  This  pin  is  hardened  and  lapped  smooth ; it  is 
then  driven  home.  The  seat  or  bearing  for  the  fulcrum  pin 
is  shown  in  view  (e).  A slot  g,  about  two-thirds  the  diam- 
eter of  the  pin  in  width,  is  cut  to  a depth  sufficient  to  have 
the  pin  clear  the  bottom  of  it.  The  upper  edges  of  the  slot 
are  slightly  beveled;  the  fulcrum  pin  rests  on  these  two 
edges.  It  is  held  down  to  its  seat  by  the  straddle  spring 
which,  by  reason  of  its  bearing  on  the  lever  between  the 
fulcrum  and  the  point  of  contact  at  the  feeler,  holds  the 
fulcrum  pin  down,  prevents  any  lost  motion,  takes  up  any 
wear,  and  also  causes  the  lever  to  follow  any  sliding  motion 


TOOLMAKING. 


17 


§ 25 

of  the  feeler.  The  straddle  spring  is  shown  in  view  (d). 
It  should  be  a rather  stiff  spring;  if  made  of  the  size  shown 
in  the  drawing,  it  should  be  made  from  sheet  steel  tV  inch 
thick. 

24.  Testing  Work. — Suppose  it  is  desired  to  test  a 
piece  of  work  to  find  out  if  it  runs  true  on  dead  centers. 
Place  the  work  between  the  centers  of  the  lathe,  and,  after 
attaching  the  indicator  to  its  holder,  which  is  shown  in  Fig.  6, 
adjust  it  so  that  the  feeler  will  bear  hard  on  the  work  to  be 
tested  and  be  about  perpendicular  to  the  surface  of  the  work. 
Rotate  the  work  between  the  centers  by  hand  and  watch 
the  end  of  the  long  arm.  If  it  moves,  it  indicates  one  or 
both  of  two  things:  (1)  The  work  may  not  be  cylindrical; 
(2)  the  work  may  be  eccentric  in  regard  to  the  centers  on 
which  it  has  been  finished. 

A good  idea  of  the  kind  of  error  may  be  formed  by  care- 
fully watching  the  movement  of  the  end  of  the  lever.  If  it 
vibrates  steadily  just  once  for  each  revolution  of  the  work, 
the  latter  is  most  likely  to  be  round,  but  not  central  in 
regard  to  its  centers.  If  the  pointer  moves  in  jumps,  i.  e., 
makes  several  vibrations  during  one  revolution,  the  work  is 
most  likely  to  be  out  of  round  and  it  may  also  be  eccentric. 
To  test  its  roundness,  caliper  it  in  a number  of  directions, 
preferably  with  a micrometer.  When  the  work  is  eccentric, 
it  can  often  be  made  central  in  regard  to  its  centers  by  care- 
fully lapping  the  center  or  centers  with  a brass  lap  charged 
with  emery,  provided  the  error  is  very  small,  say  .0005  inch. 
When  the  end  of  the  long  arm  remains  stationary,  it  shows 
the  work  to  be  both  round  and  concentric  with  its  centers. 

25.  The  indicator  may  be  applied  to  a hole  in  a piece 
of  work  held  in  the  chuck  or  on  the  face  plate,  for  the 
purpose  of  finding  out  if  the  axis  of  the  hole  coincides 
exactly  with  the  axis  of  the  spindle;  in  other  words,  to  find 
out  if  the  hole  runs  true.  If  the  hole  is  too  small  to  admit 
the  feeler  of  the  indicator,  grind  up  a cylindrical  plug  to  fit 
the  hole  nicely,  and  apply  the  indicator  to  the  outside  of  the 
cylinder.  The  indicator  may  also  be  applied  to  the  face  of 


18 


TOOLMAKING. 


25 


work,  to  see  if  it  has  been  faced  true  or  runs  true  sidewise. 
Likewise,  it  is  of  great  assistance  in  rechucking  or  resetting 
cylindrical  work  that  is  required  to  be  chucked  with  great 
accuracy. 

26.  The  particular  design  of  indicator  here  shown, 
being  removable  from  its  holder,  can  be  attached  to  a sur- 
face gauge  and  may  then  be  used  for  testing  the  parallelism 
of  straight  surfaces.  As  is  well  known,  it  is  very  difficult  to 
measure  the  parallelism  of  straight  surfaces  when  they  are 
far  apart;  in  many  cases  calipers  cannot  be  applied  at  all. 
For  instance,  consider  the  piece  shown  in  Fig.  4.  The 

question  arises  as  to  whether 
the  plane  of  the  circular  ring 
at  a is  parallel  to  the  plane 
of  b.  Evidently,  this  cannot 
be  measured  by  calipering. 
But  if  the  indicator  is  attached 
to  a surface  gauge,  the  work 
may  be  placed  on  a surface 
plate  and  the  feeler  brought 
in  contact  with  the  ring  a.  If  its  pointer  remains  stationary 
while  the  feeler  is  moved  around  the  ring,  the  surfaces  are 
parallel. 

27.  In  order  that  a small  motion  of  the  end  of  the 
pointer  will  be  visible,  it  is  necessary  to  have  some  station- 
ary point  near  it.  The  writer  has  used  for  this  purpose  a thin 
metal  disk  with  a piece  of  soft  brass  wire,  pointed  at  the  end, 
soldered  to  it.  The  disk  was  placed  between  the  joint  of  the 
holder  and  the  joint  end  of  the  indicator;  the  brass  wire  was 
then  bent  to  the  shape  required.  If  desired,  some  more 
elaborate  construction  may  be  employed. 

28.  Construction  of  a Center  Indicator. — The  cen- 
ter indicator  shown  full  size  in  Fig.  5 is  intended  to  aid  in 
the  proper  location  of  work  that  is  to  be  chucked  so  that  a 
center  punch  mark  will  coincide  with  the  axis  of  the  live 
spindle  of  the  lathe;  that  is,  run  true.  The  tool  is  essen- 
tially a lever  with  a long  and  a short  arm  turning  about  a 


TOOLMAKING. 


19 


§ 25 

ball  joint  as  a fulcrum.  The  indicator  is  clamped  to  the  tool 
holder  shown  in  Fig.  6,  which  is  held  in  the  tool  post  of  the 
lathe;  the  carriage  is  then  run  forwards  until  the  pointed 
end  of  the  short  arm  bears  lightly  in  the  center  punch  mark 
in  the  work.  The  part  a is  made  thin  so  as  to  form  a spring 
that  will  hold  the  pointer  in  the  center  punch  mark.  If,  on 
revolving  the  headstock  spindle,  it  is  found,  that  the  end  of 


the  long  arm  moves  in  a circle,  it  shows  the  center  punch 
mark  is  not  in  the  axis  of  the  spindle,  and  the  work  needs 
moving  until  the  end  of  the  pointer  remains  stationary 
when  the  spindle  with  work  attached  to  it  is  revolved. 
It  is  necessary  to  have  some  stationary  point  by  which  to 
observe  the  motion  of  the  pointer;  the  dead  center  is  the 
most  convenient  point  to  use. 


20 


TOOLMAKING. 


25 


29.  If  the  indicator  is  connected  to  a holder  in  such  a 
manner  that  it  can  be  swiveled  up  and  down,  it  can  readily 
be  used  in  all  sizes  of  lathes.  The  center  indicator  shown 
possesses  the  advantage  that  there  are  no  joints,  and  its 
accuracy  is  not  disturbed  by  wearing  of  the  joints.  Fur- 
thermore, the  pointer  is  adjustable  for  different  degrees  of 
sensitiveness;  a small  setscrew  in  the  ball,  a section  of 
which  is  shown  separately,  is  used  for  clamping  the  pointer 
and  ball  together.  It  is  scarcely  advisable  to  make  the 
pointer  longer  than  15  inches;  this  length  will  be  found  to 
answer  very  well  indeed.  If  made  longer,  the  tool  will  be 
affected  too  much  by  the  vibration  of  the  machine. 

The  pointer.,  the 


clamping  bolt  cy  by  means  of 


bail,  and  the  head  a 
should  be  made  of  tool 
steel  and  afterwards 
hardened.  The  head  a 
must  be  drawn  to  a 
spring  temper,  since 
it  serves  as  a spring. 
The  ball  and  the  end 
of  the  pointer  may  be 
drawn  to  a straw  color. 
Grind  together  the  ball 
and  the  seat  in  the 
head,  using  the  finest 
flour  emery.  The 
shank  b may  be  made 
of  machinery  steel  and 
case-hardened. 


30.  Holder  for  In- 
dicators.— The  hold- 
er shown  in  Fig.  6 is 
made  of  tool  steel.  Its 
head  a has  a cylindrical 
hole  b to  receive  the 
which  the  indicators  are 


TOOLMAKING. 


21 


§25 

attached.  The  head  has  a cylindrical  shank  closely  fitted  to 
a hole  in  the  holder  proper.  The  holder  is  split  at  the  front 
end;  a clamping  bolt  d allows  the  head  a to  be  locked  in  any 
position  after  rotation  to  the  desired  place.  The  combina- 
tion of  two  joints  allows  a movement  of  the  indicator  in  two 
planes  perpendicular  to  each  other;  hence,  the  indicator  can 
be  swung  through  a very  wide  range  of  positions,  and  is 
thus  adapted  to  almost  any  size  of  lathe  and  any  kind  of 
work  conceivable.  It  is  advisable  to  harden  the  holder  at  a 
rather  low  heat,  and  then  draw  it  to  a spring  temper. 


CUTTING  TOOLS  AND  APPLIANCES. 


DESIGN  AND  CONSTRUCTION  OF  TAPS. 


FLUTES. 

31.  Number  of  Flutes. — In  order  to  provide  cutting 
edges,  and  also  to  provide  a place  for  the  reception  of  the 
chips,  taps  are  fluted.  It  is  almost  the  universal  practice 
today  to  cut  taps,  independent  of  their  size,  up  to  and 
including  2-J-  inches  diameter,  with  four  flutes.  For  larger 
sizes,  practice  varies.  Some  toolmakers  advocate  five  or 
more  flutes  for  sizes  above;  others  retain  four  flutes  for  all 
sizes.  Generally  speaking,  four  flutes  will  usually  prove 
sufficient  and  satisfactory  for  all  taps  that  cut  a full  thread 
of  the  right  diameter  in  one  operation.  Special  taps,  or 
hobs,  as  they  are  often  called,  for  tapping  screw-cutting 
dies  are  made  with  from  six  to  eight  flutes;  they  are  not 
intended  to  cut  a full  thread  at  one  passage,  but  rather  to 
finish  out  to  size  the  hole  in  the  die  that  has  previously  been 
tapped  with  a slightly  smaller  tap. 

32.  Forms  of  Flutes. — There  are  two  different  forms 
of  fluting  in  common  use,  shown  in  Fig.  7 at  ( a ) and  ( b ), 
respectively.  The  form  shown  at  (a)  is  considered  by  many 


22 


TOOLMAKING. 


25 


as  the  better  form,  since  it  makes  not  only  the  stronger  tap, 
but  also  prevents  the  cracking  of  the  tap  lengthwise  in 
hardening,  owing  to  the  absence  of  relatively  sharp  corners 


where  a crack  could  start.  The  curve  of  the  groove  is  com- 
posed of  two  arcs  tangent  to  each  other;  the  large  arc,  as 
b , may,  for  a four-fluted  tap,  have  a radius  equal  to  the 
diameter  of  the  tap,  and  the  small  arc  c may  have  a radius 
of  one-sixth  of  the  diameter.  These  proportions  are  approx- 
imate and  vary  somewhat,  not  only  with  different  makers, 
but  also  on  account  of  the  inexpediency  of  having  a different 
cutter  for  each  different  size  of  tap.  In  practice,  one  cutter 
will  be  made  to  answer  for  several  sizes. 

The  fluting  shown  at  ( b ) is  probably  the  one  in  most  com- 
mon use,  although  it  does  not  make  as  strong  nor  as  easy 
working  a tap.  In  order  not  to  weaken  the  tap  too  much, 
the  land  a must  be  left  wider  than  it  is  in  Fig.  7 (a) ; this 
produces  a greater  friction  in  tapping.  The  sides  of  the 
flute  are  perpendicular  to  each  other; 
the  corner  may  have  a radius  of  one- 
eighth  of  the  diameter  of  the  tap. 

In  both  forms  of  fluting,  it  is  the 
common  practice  to  make  the  cut- 
ting edges  radial,  as  shown  by  the 
dotted  lines  in  Fig.  7.  This  answers 
very  well  indeed  for  general  work.  If 
a tap  is  to  be  used  entirely  for  brass, 
and  especially  for  brass  castings,  the 


TOOLMAKING. 


23 


§ 25 

cutting’  edge  may  be  slightly  advanced  in  the  direction  of 
cutting  parallel  to  a radial  line,  as  shown  in  Fig.  8.  This 
will  give  it  a slight  negative  rake  and  cause  it  to  cut  more 
smoothly  and  with  less  liability  of  chattering.  The  amount 
that  the  cutting  edge  is  advanced  need  not  be  very  large; 
it  may  be  from  one-sixteenth  to  one-tenth  of  the  diameter 
of  the  tap.  Taps  that  are  to  be  used  for  general  work  on 
all  kinds  of  metal  usually  have  their  cutting  edges  radial. 


HAND  TADS. 

33.  Design. — As  the  name  implies,  liand  taps  are 
intended  for  tapping  holes  by  hand.  Since  it  is  rather  dif- 
ficult to  use  the  tap  without  throwing  a sideward  strain  on 
it,  in  consequence  of  which  the  tapped  hole  will  be  larger  at 
the  end  where  the  tap  was  started,  the  construction  should 
be  such  that  it  will  counteract  this  tendency  as  much  as 
possible.  This  is  done  by  making  the  lands  rather  wide  and 
giving  no  relief  to  the  thread  back  of  the  cutting  edge.  The 
width  of  the  lands  for  a four-fluted  tap  when  made  with 
flutes,  as  shown  in  Fig.  7 (a),  may  be  two-tenths  the  diam- 
eter of  the  tap.  When  fluted  with  four  flutes,  as  shown  in 
Fig.  7 ( b ) and  Fig.  8,  the  width  a of  the  lands  may  be  about 
one-fourth  the  diameter  of  the  tap.  The  square  on  the  end 
of  the  tap  intended  to  receive  the  tap  wrench  is  generally 
placed  so  that  the  corners  are  in  line  with  the  cutting 
edges. 


34.  Making  a Hand  Tap. — For  a straight  tap,  select 
steel  slightly  larger  in  diameter,  say  y1^-  inch,  for  sizes  up  to 
^-inch;  -J.  inch  for  sizes  up  to  1 ^ inches;  and  T3y  to  \ inch 
larger  for  sizes  above.  Have  it  well  annealed,  preferably  in 
slaked  lime.  Turn  the  shank  and  tap  body  to  size,  then 
mill  or  file  the  square  and  cut  the  thread  in  the  lathe.  The 
thread  should  be  cut  as  smooth  as  possible  ; many  tool- 
makers  prefer  to  use  the  single-pointed  tool  for  roughing  out 
to  within  .002  or  .003  inch  of  the  correct  size  and  then 


24 


TOOLMAKING. 


25 


finish  it  with  a chaser.  On  small  taps,  but  only  when  accu- 
racy of  pitch  is  not  essential,  the  thread  may  be  cut  with  a 
die.  If  the  die  is  in  good  condition,  a very  good  thread  can 
be  cut  if  plenty  of  oil  is  used  in  cutting;  however,  as  with  all 
dies  that  feed  themselves,  the  pitch  of  the  thread  cut  will  be 
coarser  than  the  pitch  of  the  thread  of  the  die.  The  thread 
having  been  cut,  chamfer  the  end  in  the  lathe  an  amount 
depending  on  whether  the  tap  is  to  be  a taper  tap,  plug 
tap,  or  bottoming  tap.  The  tap  is  now  ready  for  fluting. 
This  can  best  be  done  in  the  milling  machine,  holding  the 
tap  between  the  centers  or  in  the  universal  chuck,  accord- 
ing to  size.  The  cutter  is  set,  by  trial,  to  cut  the  correct 
depth  of  flute;  large  taps  may  require  several  cuts. 

The  flutes  having  been  cut,  the  cutting  edges  will  have  to 
be  filed  up  a little  on  the  face  with  a rather  fine  file  to 
remove  the  burrs  left  by  the  milling  cutter,  and  if  the  tap  is 
over  \ inch,  it  had  better  be  backed  off  by  filing.  The 
chamfered  ends  must  be  given  clearance  by  filing.  The 
size,  and,  preferably,  the  number  of  threads  also,  having 
been  stamped  on  the  shank,  the  tap  is  ready  for  hardening. 
To  harden  it,  the  safest  way  is  to  heat  it  inside  of  a piece 
of  gas  pipe,  frequently  turning  the  latter  and  changing  its 
position.  The  danger  of  overheating  and  burning  the  steel, 
and  of  unequal  heating,  is  greatly  lessened  thereby.  The 
tap  should  be  hardened  at  as  low  a heat  as  will  make  it  hard 
enough  so  that  a file  will  not  “touch.”  it,  dipping  it  ver- 
tically into  clear  water  a little  beyond  the  threaded  part.  It 
may  then  be  ground  in  the  flutes  on  an  emery  wheel  to 
sharpen  the  teeth  and  make  it  bright  for  tempering.  Draw 
it  to  a good  straw  color  evenly  all  over,  holding  it  some 
distance  above  the  fire.  When  an  emery  wheel  is  not 
available,  the  cutting  edges  must  be  made  sharp  before 
hardening  by  filing  with  a fine  file.  The  tap  may  be 
brightened  in  the  flutes,  after  hardening,  by  grinding  or  by 
emery  cloth,  using  care  that  the  emery  cloth  does  not 
touch  the  cutting  edges;  if  it  does,  it  will  dull  them  more 
or  less.  It  is  best,  however,  not  to  use  any  emery  cloth 
on  a tap. 


25 


TOOLMAKING. 


25 


35.  Effect  of  Hardening. — If  the  pitch  of  the  thread 
and  its  diameter  are  measured  after  hardening,  it  will  usu- 
ally be  found  that  the  pitch  and  the  diameter  have  changed 
a small  amount.  In  a few  instances,  the  tap  will  measure 
the  same  as  before.  There  is  no  known  way  of  preventing 
this  change,  which  is  due  to  hardening.  It  can  be  mini- 
mized by  a slow,  careful,  and  even  heating,  combined  with 
a hardening  at  as  low  a heat  as  will  be  sufficient  to  make 
the  tap  hard.  Fortunately,  the  amount  of  change  rarely 
exceeds  two-thousandths  of  the  length  and  diameter,  and  is 
negligible  for  nearly  all  work. 

36.  Straightening  Taps. — When  taps  are  rather 
long,  they  will  usually  become  crooked  in  hardening  and 


Fig.  9. 

tempering.  They  can  be  straightened  as  follows:  Place  the 
tap  between  the  centers  of  the  lathe;  fasten  a piece  of  metal 
with  a square  end  in  the  tool  post  and  place  it  against  the 


26 


TOOLMAKING. 


§ 25 


highest  point  of  the  convex  side,  as  shown  in  Fig.  9.  Now, 
with  a Bunsen  burner  or  an  alcohol  lamp,  heat  the  tap, 
which  has  been  previously  covered  with  lard  oil,  until  the  oil 
commences  to  smoke.  Then,  by  means  of  the  cross-feed, 
slowly  force  the  tap  over  until  it  is  a little  crooked  the  other 
way  and  quickly  cool  it  while  between  the  centers.  By 
repeating  this  operation,  it  may  be  straightened  very  nicely. 
The  amount  the  tap  must  be  forced  over  can  only  be  ascer- 
tained by  practical  experience.  No  attempt  can  be  made  to 
give  a rule  for  it.  Other  hardened  and  sprung  work  may  be 
straightened  in  the  same  manner. 

The  tap  should  be  straightened  before  drawing  the  tem- 
per. String  solder  may  be  used  in  place  of  oil  to  test  the 
temperature  when  heating  the  tap.  As  quick  as  the  solder 
melts,  the  tap  is  hot  enough. 


MACHINE  TAPS. 

37.  Machine  taps  are  intended  for  use  in  tapping  ma- 
chines, in  the  turret  lathe,  and  for  similar  work.  Since  these 
taps  are  intended  to  be  guided  axially 
by  their  attachments,  the  lands  can  be 
made  narrower  than  in  hand  taps,  and 
relief  can  be  given  to  the  teeth,  which 
causes  them  to  cut  more  freely.  Relief 
is  given  by  filing  the  thread  back  of  the 
cutting  edge  until  the  tap  has  the  form 
shown  in  Fig.  10.  Very  little  filing  is 
fig.  io.  necessary;  it  is  not  advisable  to  give 

too  much  relief,  since,  in  backing  the  tap  out,  chips  are 
liable  to  be  drawn  in  between  the  work  and  the  lands. 


TAPER  TAPS. 

38.  Relief. — In  making  a taper  tap,  attention  must 
be  paid  to  two  points  that  are  frequently  overlooked,  and  in 
consequence  of  which  the  tap,  though  finely  made  otherwise, 
will  produce  poor  work.  These  points  are:  (1)  The  teeth 
must  be  relieved  back  of  the  cutting  edge;  and  (2)  a taper 


§25 


TOOLMAKING. 


27 


tap  cannot  be  cut  to  correct  pitch  by  setting  the  tailstock 
over  and  gearing  up  for  the  right  number  of  threads  per 
inch.  A trial  of  a taper  tap  not  relieved  in  the  thread, 
especially  if  the  taper  is  large,  will  immediately  show  that 
the  tap,  instead  of  cutting  the  metal,  will  squeeze  it.  This 
is  due  to  the  fact  that  the  sides  of  the  thread  at  the  back  of 
the  lands  drag  against  the  work,  thus  preventing  the  cut- 
ting edges  from  cutting.  The  threads  are  usually  backed 
off  with  a three-square  file;  manufacturers  of  taps  use  a 
special  machine  that  relieves  the  thread  in  the  process  of 
cutting  it. 

39.  Errors. — In  order  that  the  tap  may  have  the  cor- 
rect pitch  of  thread,  it  must  be  cut  by  the  use  of  a taper 
attachment.  When  a taper  tap  is  cut  in  a lathe  not  fitted 
with  a taper  attachment,  it  is  done  by  setting  over  the  tail- 
stock  center.  Two  errors  are  then  introduced  that  become 
more  pronounced  as  the  taper  is  made  larger.  In  the 
first  place,  the  pitch  will  be  finer;  in  the  second  place,  the 
thread,  instead  of  being  true,  will  be  drunken.  Neither  one 
of  these  errors  can  be  corrected  very  readily.  The  second 
error  is  due  to  the  fact  that,  in  taper  turning  with  the  tail- 
stock  set  over,  the  work  does  not  turn  with  a uniform 
angular  velocity,  while  the  cutting  tool  advances  along  the 
work  with  a uniform  linear  velocity. 

When  the  taper  is  slight,  the  change  in  pitch  and  the 
drunkenness  of  the  thread  is  ordinarily  imperceptible  to  the 
eye ; with  tapers  of  f inch  per  foot,  the  errors  become  sen- 
sible and  increase  rapidly  as  the  taper  becomes  larger.  For 
these  reasons,  taper  taps  should  always  be  cut  with  the 
taper  attachment.  If  none  is  available,  there  is  nothing 
left  except  to  set  the  tailstock  over.  The  thread  should 
then  be  well  relieved;  this  will  make  the  tap  cut  free,  but 
will  correct  neither  the  pitch  nor  the  drunkenness  of  the 
thread.  In  cutting  the  thread  on  a taper  tap,  the  threading 
tool  should  be  set  square  with  the  axis  of  the  tap.  This  is 
the  practice  of  manufacturers  and  is  well  worthy  of  general 
adoption. 


28 


TOOLMAKING. 


§25 


40.  In  order  that  the  toolmaker  may  determine  whether 
the  error  in  pitch  introduced  by  setting  over  the  tailstock  is 
of  sufficient  importance  to  prohibit  this  method,  the  table 
below  is  given.  In  this  table,  the  figures  in  the  second  col- 
umn represent  the  length  along  the  center  line  of  the  tap, 
in  ten-thousandths  of  an  inch,  for  1 inch  measured  along  the 
surface  of  the  tap. 

TABLE  OF  ERRORS  IN  TAPER  TAPS. 


Taper. 

Length 
Along  Axis. 

Taper. 

Length 
Along  Axis. 

| inch  per  foot. 

.9999 

l£  inches  per  foot. 

.9980 

£ inch  per  foot. 

.9999 

If  inches  per  foot. 

.9973 

T5g  inch  per  foot. 

.9999 

2 inches  per  foot. 

.9965 

f inch  per  foot. 

.9998 

2£  inches  per  foot. 

.9946 

-fa  inch  per  foot. 

.9998 

8 inches  per  foot. 

.9922 

inch  per  foot. 

.9997 

3|  inches  per  foot. 

.9895 

£ inch  per  foot. 

.9995 

4 inches  per  foot. 

.9863 

1 inch  per  foot. 

.9991 

Note. — The  word  taper  is  defined  in  a different  manner  by  different 
persons;  it  will  here  be  taken  to  mean  the  difference  in  diameters  per 
foot  of  length  measured  along  the  axis.  This  definition  is  in  accord- 
ance with  the  most  general  practice. 


HOBS. 

41.  Design  and  Use.  — Taps  made  for  cutting  the 
threads  in  solid  and  split  dies  for  screw  cutting  are  called 
hobs.  They  differ  from  ordinary  taps  chiefly  in  having 
more  flutes;  they  are  usually  given  from  six  to  eight  flutes. 
When  hobs  are  to  be  used  for  solid  dies,  they  must,  of  course, 
be  of  exact  diameter.  When  used  for  dies  adjustable  through 
quite  a range,  it  is  advisable  to  make  them  larger.  Their 
diameter  may  then  be  twice  the  depth  of  thread  plus  the 
diameter  of  bolt.  It  is  recommended  that  the  diameter  of 
the  hob  should  not  be  made  larger  than  just  given.  Cut- 
ting an  adjustable  die  with  a hob  larger  than  the  screw  to 
be  cut  with  it,  will  have  the  effect  of  giving  relief  to  the 


TOOLMAKING. 


29 


§ 25 

threads  of  the  die  back  of  the  cutting  edges.  In  conse- 
quence of  this  relief,  which  in  ordinary  dies  cannot  readily 
be  given  in  any  other  manner,  the  die  will  cut  much  more 
easily  and  cleanly.  Hobs  are  advantageously  used  in  con- 
nection with  a leading  tap  slightly  smaller  in  diameter. 
This  relieves  the  hob  of  the  most  severe  duty,  and  hence  a 
smoother  and  truer  hole  will  be  tapped  by  it. 

When  making  a hob,  it  must  always  be  remembered  that 
the  perfection  of  the  screw  made  by  the  die  the  hob  is  in- 
tended for,  depends  primarily  on  the  hob;  and  hence  this 
should  be  made  as  perfect  as  conditions  permit.  ' Any  poor 
workmanship  in  the  thread  of  the  hob  will  be  duplicated 
in  the  die,  and  usually  in  a more  emphatic  manner.  A 
poorly  cut  die  will  naturally  produce  a poor  screw  thread. 
When  tapping  a die  with  a hob, plenty  of  oil  should  be  used 
and  care  should  be  taken  to  see  that  the  flutes  do  not  be- 
come clogged  with  chips.  Some  persons  do  not  relieve  the 
hobs  that  are  intended  for  straight  dies,  but  taper  hobs 
should  always  be  relieved,  for  the  same  reason  as  taper  taps. 

The  term  “ hob  ” is  also  applied  to  the  milling  cutter  used 
for  cutting  the  teeth  of  worm-wheels  to  correct  shape.  This 
style  of  hob  will  be  treated  of  under  the  heading  of  “ Mill- 
ing Cutters.” 

42.  Chaser  Hobs. — Hobs  for  making  chasers  are  made 
straight.  They  need  not  be  longer  than  three  times  the 
width  of  the  widest  chaser  that  is  to  be  cut  by  them.  Nu- 
merous flutes  are  required,  and,  preferably,  should  be  spaced 
a little  unevenly.  As  they  are  intended  to  be  used  between 
the  centers  of  a hand  lathe,  they  should  be  provided  with 
liberal-sized  centers.  A shank  long  enough  to  take  a dog 
should  be  provided.  For  threads  from  40  per  inch  to  8 per 
inch,  a good  size  is  1^  inches  diameter,  with  the  thread  about 
2 inches  long,  and  the  shank  1|-  inches  long.  About  twenty 
flutes  may  be  cut  with  a 60-degree  cutter,  making  the  cut- 
ting edges  radial.  Since  the  excellence  of  the  chaser  de- 
pends on  the  hob,  the  thread  should  be  cut  as  perfect  and 
smooth  as  possible.  After  hardening  at  a low  heat,  draw 


TOOLMAKING. 


30 


§ 25 


the  hob  uniformly  to  a full  straw  color.  When  using  it, 
adjust  the  rest  to  such  a height  that  the  upper  side  of  the 
chaser  will  be  about  y1^  inch  above  the  height  of  the  cen- 
ter. The  hob  will  then  cut  the  teeth  into  the  chaser  with 
sufficient  relief  to  make  it  cut  free.  The  chaser  itself  may 
be  drawn  to  a pale  straw  color. 


ADJUSTABLE  TAPS. 

43.  Design. — Where  holes  have  to  be  tapped  to  a very 
exact  size,  as  is  often  required  in  work  done  in  large  quan- 
tities under  the  interchangeable  system,  it  is  rather  hard  to 
produce  solid  taps  that  will  tap  the  holes  within  the  limit  of 
variation  permissible.  While  it  is  quite  feasible  to  make 
them  accurate  within  .0001  inch  when  soft,  the  change  in 
diameter  when  hardening  them  will  often  go  beyond  the  per- 
missible limit  of  variation,  especially  when  the  tap  is  larger 
than  inch.  It  is  of  very  little  use  to  try  to  make  allow- 
ance for  this  change  of  diameter,  since  nobody  can  tell 
whether  the  steel  will  contract,  expand,  or  remain  the  same 
diameter  in  hardening.  For  these  reasons,  adjustable 
taps  have  been  designed.  Some  of  these  will  cut  a full 
thread  in  one  passage  through  the  work ; others  again  can 
be  used  only  for  finishing  a hole  that  has  previously  been 
tapped  by  a leading  tap  of  slightly  smaller  diameter. 

44.  Examples  of  Adjustable  Taps.  — Adjustable 
taps  may  be  made  as  shown  in  Fig.  11.  There  are  four 

a 


a 


a 

Fig.  11. 


tool-steel  blades  a,  a inserted  in  dovetail  slots;  the  bottom 
of  the  slots  makes  an  angle  with  the  center  line,  or  axis,  of 
the  tap.  The  blades  are  confined  axially  by  two  nuts,  one 


TOOLMAKING. 


31 


§ 25 


at  each  end.  By  varying  the  position  of  these  nuts,  the  tap 
may  be  expanded  or  contracted  a slight  amount.  Taps  of 
this  kind  cannot  ordinarily  be  made  for  sizes  smaller  than 
1 inch,  since  the  shank  will  become  too  small  if  made 
smaller. 


45-  In  making  such  a tap,  the  body  should  be  turned 
first.  In  the  smaller  sizes  the  body  may  be  made  of  tool 
steel,  and  for  large  taps,  of  machinery  steel.  The  slots 
can  generally  be  cut  faster  and  better  in  the  shaper  than  in 
the  milling  machine.  Cut  a fine  thread  for  the  two  nuts 
in  the  lathe ; the  diameter  of  the  tap  body,  at  the  points  where 
the  nuts  are  located,  is  sometimes  made  small  enough  to  clear 
the  bottom  of  the  slots.  Thread  and  face  each  one  of  the  two 
nuts  at  the  same  chucking,  in  order  that  the  faces  will  be  true 
with  the  thread,  and  make  the  nuts  a good  snug  fit.  The 
blades  may  now  be  milled  or  planed  out  of  well-annealed  tool 
steel  and  then  carefully  fitted  to  the  slots.  In  order  to  make 
them  of  equal  length,  drive  them  into  the  slots  and  face 
their  ends  in  the  lathe.  They  should  fit  tightly  enough  not 
to  slip  during  facing.  Put  the  nuts  on  and  screw  the  nut 
at  the  shank  end  up  until  it  is  within  a short  distance  of  the 
shoulder.  Then  tighten  up  the  front  end  nut.  Now  turn 
the  blades  to  correct  size  (approximately) ; cut  the  thread  on 
the  blades,  using  the  lathe,  and  chamfer  the  front  end  with 
a square-nosed  tool.  Remove  the  nuts,  mark  the  blades  and 
slots  with  corresponding  marks,  drive  tlie  blades  out,  re- 
lieve the  chamfered  parts,  and  slightly  back  off  the  threads 
with  a fine  three-square  file.  The  threads  require  backing 
off  on  account  of  the  springing  of  the  tap  during  thread 
cutting  causing  the  back  edge  of  each  blade  to  be  slightly 
higher  than  the  front  or  cutting  edge.  After  relieving, 
harden  and  temper  the  blades  carefully,  drawing  them  to  a 
straw  color.  If  the  blades  should  spring  very  much,  they 
must  be  straightened  before  inserting  them  again.  Assu- 
ming the  body  to  be  of  machinery  steel,  it  may  be  well  to  case- 
harden  the  square  at  the  end.  An  adjustable  tap  is  usually 
set  to  correct  size  by  actual  trial. 


C.  S.  III.— 30 


32 


TOOLMAKING. 


25 


46.  A very  simple  form  of  adjustable  tap  is  shown 
in  Fig.  12.  This  method  of  construction  is  covered  by  a 


Fig.  12. 

patent;  the  J.  M.  Carpenter  Tap  and  Die  Company, 
Pawtucket,  Rhode  Island,  are  the  exclusive  manufacturers 
of  these  taps.  As  shown  in  the  figure,  the  tap  is  split. 
Taper-headed  screws  b allow  it  to  be  expanded,  and 
binding  screws  a , a serve  to  lock  the  two  halves  together. 

47.  Another  design  of  adjustable  tap  suitable  for  holes 
that  pass  clear  through  the  work,  or  do  not  need  to  be 
tapped  close  to  the  bottom,  is  shown  in  Fig.  13.  The 


Fig.  13. 

tap  is  split  longitudinally;  the  two  halves  can  be  forced 
apart  by  a centrally  located  screw  a having  a tapering  head. 
After  setting  it,  the  two  halves  of  the  tap  are  locked  to- 
gether by  setting  up  the  nut  b , which  has  a beveled  recess 
that  engages  the  conical  projection  at  the  front  end  of  the 
tap.  While  locking  the  nut,  the  central  screw  must  be  pre- 
vented from  turning  by  inserting  a screwdriver  into  its  slot 
and  holding  it.  The  nut  may  be  made  hexagonal  in  form 
at  its  front  part,  as  shown,  or  have  radial  holes  drilled  in  its 
circumference.  In  the  latter  case,  a spanner  must  be  made 
for  it.  In  making  such  a tap,  it  is  advisable  to  cut  the 
thread  and  flute  the  tap  before  splitting  it.  It  may  be  slot- 
ted slightly  beyond  its  threaded  part,  the  slot  terminating  in 
&hole  drilled  perpendicular  to  the  axis, 


§25 


TOOLMAKING. 


33 


MULTIPLE-THREADED  TAPS. 

48.  Occasionally,  multiple-threaded  taps  are  re- 
quired. If  these  are  intended  to  cut  a full  thread  in  one 
operation,  the  lands  back  of  the  cutting  edges  must  be  well 
relieved  to  allow  the  tap  to  cut  freely;  if  this  is  not  done, 
the  force  required  for  tapping  may  be  sufficient  to  break  the 
tap.  Generally  speaking,  it  is  better  to  chase  the  threads  in 
the  hole  to  be  tapped  and  use  the  tap  for  finishing  only. 


SQUARE-THREADED  TAPS. 

49.  Square-threaded  taps  may  be  fluted  in  the  same 
manner  as  V-threaded  taps.  If  intended  to  cut  a full  thread 
in  one  operation,  the  lands  must  be  well  backed  off,  other- 
wise the  amount  of  force  required  for  tapping  will  be  exces- 
sive. When  used  merely  for  sizing  holes  in  which  the  thread 
has  been  roughed  out,  very  little  backing  off  is  necessary. 


LEFT-HANDED  TAPS. 

50.  If  a left-handed  tap  is . required,  it  may  be 
designed  and  made  in  the  same  manner  as  a right-handed 
tap,  except  that  the  flutes  are  to  be  cut  in  a way  the  reverse 
of  that  used  for  a right-handed  tap.  All  remarks  previously 
made  regarding  the  number  of  flutes  and  the  backing  off  of 
the  lands  apply  to  left-handed  taps  as  well.  It  is  a good 
plan  to  stamp  left-handed  taps  with  a large  L on  the  shank, 
to  call  attention  to  the  fact  of  their  being  left-handed.  This 
is  to  be  done  not  on  account  of  machinists  not  being  able  to 
detect  the  difference,  but  rather  on  account  of  unskilled 
helpers  failing  to  distinguish  between  right-handed  and  left- 
handed  taps 


COLLAPSING  TAPS. 

51.  Purpose  of  Collapsing;  Taps. — Taps  so  con- 
structed that  the  blades  forming  the  cutting  edges  can  be 
moved  radially  at  will  toward  or  from  the  center,  are  called 
collapsing  taps.  They  are  used  quite  largely  for  work 


34 


TOOLMAKING. 


§25 


done  in  the  turret  lathe,  when  the  hole  to  be  tapped  exceeds 
inches  in  diameter.  Their  chief  advantage  is  that  they 
need  not  be  turned  back  to  withdraw  them  from  the  tapped 
hole;  the  blades  are  drawn  in  enough  toward  the  center  to 
clear  the  thread,  and  the  tap  can  then  be  withdrawn  by  an 
axial  motion.  As  a matter  of  course,  nearly  all  the  time 
required  to  wind  an  ordinary  tap  back  is  saved.  Since 
a collapsing  tap  is  quite  an  expensive  tool,  its  use  is 
limited  by  commercial  considerations  to  work  done  in  large 
quantities. 


52.  Design  of  a Collapsing  Tap. — A simple  collaps- 
ing tap  designed  for  tapping  a taper  hole  in  brass  castings  is 

shown  in  Fig.  14.  For 
this  reason,  the  cutting 
edges  of  the  blades  are 
advanced  in  the  direc- 
tion of  cutting ; that  is, 
theyare  given  negative 
rake.  The  shank  A is 
fitted  to  the  turret. 
The  end  of  the  shank 
is  bored  out  cylindrical 
to  receive  the  tap 
body  £,  in  which  four 
dovetail  grooves  are 
cut,  to  which  the  blades 
or  chasers  are  fitted. 
A circular  groove  d\ 
having  a square  cross- 
section  [see  Fig.  14  (r)] , 
receives  the  lugs  d , d and  confines  the  chasers  longitudi- 
nally. The  body  of  the  tap  is  prevented  from  rotating, 
by  a pin  C passing  through  it.  This  pin,  while  the  tap  is 
cutting,  rests  against  the  lower  ends  of  the  helical  slots  F 
and  F'.  When  the  hole  has  been  tapped  to  the  desired 
depth,  the  pin  C is  turned  in  the  direction  of  the  arrow. 
The  pin  then  follows  the  helical  slots  and  the  body  B 


Fig.  14. 


§ 25 


TOOLMAKING. 


35 


is  drawn  into  the  shank;  since  the  dovetail  grooves  in 
which  the  chasers  work  are  at  an  inclination  to  the  axis,  the 
chasers  are  drawn  together  and  the  tap'  can  be  withdrawn. 
To  get  it  ready  for  work  again,  the  pin  C is  turned  back. 
A tap  of  the  design  shown  in  Fig.  14  may  be  used  in  a 
chuck  in  the  lathQ.  When  used  for  a turret  lathe,  it  is 
almost  always  necessary  that  the  hole  is  to  be  tapped  to  the 
same  depth  in  every  piece  operated  upon.  If  this  is  the 
case,  it  should  be  used  in  connection  with  an  adjustable  dis- 
connecting tap  holder. 

53.  Making  the  Tap  Shank. — When  making  a col- 
lapsing tap  of  the  kind  shown,  the  only  thing  that  may 
prove  difficult  will  be  the  two  helical  slots.  They  are 
rather  difficult  to  produce  by  hand,  but  if  care  is  taken  to 
use  a helix  that  can  be  cut  in  the  milling  machine  by  an  end 
mill,  the  slots  are  easily  cut.  If  no  milling  machine 
adapted  for  spiral  work  is  available,  the  slots  may  be  cut  in 
the  lathe  as  follows:  Gear  the  lathe  to  cut  a thread  having 
a pitch  equal  to  one  turn  of  the  helix  adopted.  Then,  with 
a scriber  fastened  in  the  tool  post  and  the  tap  shank  between 
the  centers  and  forced  to  turn  with  the  spindle,  scribe  a fine 
line  on  the  shank  in  the  proper  place  to  represent  the  center 
line  of  the  slot.  Turn  the  work  180°  between  the  centers 
without  moving  the  headstock  spindle;  scribe  a line  again. 
Now  throw  the  leadscrew  out  of  gear  and  at  the  beginning 
and  end  of  the  slots  scribe  fine  circles  around  the  tap  body. 
At  the  intersection  of  these  circles  with  the  helical  lines, 
make  fine  center-punch  marks,  and  divide  along  these  lines 
into  a sufficient  number  of  divisions  to  drill  out  most  of  the 
stock.  Center  punch  well,  and  drill  out  the  stock,  remov- 
ing most  of  the  stock  between  the  holes  with  a keen-edged 
cape  chisel.  The  slots  may  now  be  finished  by  a suitable 
planing  tool  to  be  held  in  the  tool  post  of  the  lathe.  The 
tap  body  is  placed  between  the  centers,  and  the  dog  prop- 
erly adjusted  to  have  the  tool  match  the  slot.  A wooden 
wedge  is  then  driven  in  between  the  tail  of  the  dog  and  the 
side  of  the  slot  in  the  face  plate  that  drives  it;  rotating  the 


36 


TOOLMAKING. 


§25 

leadscrew  by  hand  will  then  cause  the  tool  to  travel  along 
the  tap  body,  and,  if  fed  in  by  means  of  the  cross  feed-screw, 
it  will  cut  out  the  slot.  The  planing  tool  is  preferably  made 
so  as  to  plane  both  sides  of  the  slot  at  once.  The  opposite 
slot  may  be  finished  in  the  same  manner. 

54.  Collapsing  taps  may  be  made  in  a variety  of  de- 
signs to  suit  different  kinds  of  work.  Thus,  where  bottom- 
ing holes  are  to  be  tapped,  the  blades  may  be  arranged  to 
collapse  by  means  of  a centrally  located  movable  stop  within 
the  tap  body  coming  in  contact  with  the  bottom  of  the  hole; 
the  stop  when  moving  back  then  draws  the  blades  inward. 

For  some  work  it  may  be  advantageous  to  design  a col- 
lapsing tap  on  the  lines  of  the  ordinary  scroll  chuck,  or  the 
geared  three-jawed  or  four-jawed  automatic  chuck.  These 
designs  will  readily  suggest  others. 


RELEASING  TAP  HOLDERS. 

55.  Purpose  and  Design. — In  screw-machine  and 
turret-lathe  work,  when  holes  are  to  be  tapped  to  a uniform 
depth,  it  is  advisable  to  use  a tap  holder  that  will  automatic- 
ally release  the  tap  from  the  holder  as  soon  as  the  hole  has 
been  tapped  to  the  proper  depth.  Such  a holder  will  allow 


fig.  15. 


of  rapid  tapping,  and,  when  properly  adjusted,  obviates 
breakage  of  taps  through  striking  the  bottom  of  the  hole. 

A very  common  and  highly  efficient  releasing  tap  holder 
is  that  shown  in  Fig.  15,  which  is  especially  adapted  to  screw- 
machine  and  turret-lathe  work.  It  consists  essentially  of 


TOOLMAKING. 


37 


§25 

two  pieces.  The  sleeve  a has  a shank  that  fits  one  of  the 
tool  holes  of  the  turret.  The  tap  holder  proper  is  free  to  slide 
longitudinally  within  the  sleeve  a certain  amount;  when  the 
clutch  pinsc  and  d are  disengaged,  it  is  free  to  rotate  within 
the  sleeve.  The  end  of  the  tap-holder  shank  carries  the 
backing-out  pin  e,  which  is  so  located  that  when  the  clutch 
pins  c and  d will  just  clear  each  other,  it  will  be  from  ■§■  to 
J inch  away  from  the  helically  formed  end  of  a.  The  end  b 
of  the  tap  holder  may  be  made  in  a variety  of  ways  to  suit 
the  purpose.  The  simplest  way  is  to  make  it  as  shown;  the 
tap  shank  fits  the  hole  and  is  held  from  turning  by  the  set- 
screw. If  thus  made,  its  use  is  obviously  limited  to  taps 
having  the  same  shank  diameter.  To  make  it  adapted  to  all 
sizes  of  taps,  the  end  b may  be  a universal  chuck;  the  holder 
then  becomes  a universal  releasing  tap  holder. 

56.  Operation.  — The  operation  is  as  follows:  The 
shank  a being  fastened  in  the  turret  and  the  stop-pin  c but- 
ting against  the  flange  of  a and  the  stop-pin  d preventing  b 
from  turning,  the  slide  of  the  turret  is  advanced  and  the 
tap  then  engages  the  revolving  work.  As  soon  as  the  tur- 
ret slide  comes  against  its  stop,  the  tap,  by  reason  of  being 
entered  in  the  work,  is  drawn  forwards  until  c and  d are  dis- 
engaged, when  it  is  free  to  revolve.  This  stops  further  tap- 
ping. The  spindle  of  the  machine  is  now  reversed,  which 
causes  the  work,  and  hence  the  tap,  to  turn  in  an  opposite 
direction.  The  turret  slide  is  then  withdrawn  to  the  rear; 
the  backing  pin  e during  the  backward  motion  is  guided  by 
the  helical  end  into  the  recess  of  the  sleeve  shank,  and  any 
further  revolution  of  the  tap  is  thus  arrested.  In  conse- 
quence of  this,  the  tap  is  backed  out  by  the  revolving  work. 

57.  Forming  the  Helical  End. — When  making  a 
releasing  tap  holder,  it  is  well  to  remember  that  the  helix  at 
the  end  of  the  sleeve  shank  must  be  right-handed  for  a right- 
hand  tap  and  left-handed  for  a left-hand  tap.  The  pitch  of 
the  helix  may  be  about  one  and  one-half  times  the  diameter 
of  the  stop-pin.  The  helix  is  most  readily  produced  in  the 
lathe,  gearingthe  lathe  to  give  the  proper  pitch  and  using  a 


38 


TOOLMAKING. 


§25 


square-nosed  tool  for  cutting  the  helix.  A line  may  first  be 
scribed  to  mark  the  position  of  the  helix  and  then  most  of 
the  stock  removed  by  drilling  and  chipping,  leaving  to  the 
lathe  tool  the  finishing  only. 

58.  Proportions. — The  diameter  of  the  sleeve  shank 
is  fixed  by  the  size  of  the  holes  in  the  turret  for  which  it  is 
intended,  as  is  also  its  length.  The  shank  of  the  tap  holder 
may  be  about  five-eighths  the  diameter  of  the  sleeve  shank. 
The  three  stop-pins  may  have  a diameter  equal  to  about’ 
one-third  the  diameter  of  the  tap-holder  shank.  For  small 
work,  it  is  usually  advisable  to  make  the  whole  device  of 
tool  steel. 


NUMBER  OF  TAPS  IN  SPECIAL  CASES. 

59.  Taps  for  Square  Threads. — In  tapping  square 
threads  several  taps  are  sometimes  used  in  a set,  especially 
where  the  hole  is  small  and  the  pitch  of  the  thread  coarse. 
When  the  hole  is  long  the  flutes  in  the  ordinary  tap  are  too 
small  to  carry  off  the  cuttings,  hence  more  taps  are  used, 
taking  smaller  cuts  and  having  larger  flutes. 

Sometimes  as  many  as  six  taps  are  used  in  a set  and  if 
they  run  with,  plenty  of  oil  they  will  clear  themselves  readily, 
cut  more  rapidly,  and  last  longer  without  dulling.  The  fir$t 
tap  is  sometimes  a V-thread  tap  with  the  correct  pitch,  and 
the  other  taps  take  out  the  balance  of  the  stock,  gradually 
approaching  the  square  shape  until  the  correct  size  and  form 
is  reached. 

60.  Square-Tliread  Taps  in  Brass. — Where  square- 
thread  taps  do  not  readily  clear  themselves  of  chips,  it  has 
been  found  advantageous  to  remove  some  of  the  teeth,  or 
lands,  of  the  tap.  Sometimes  every  other  tooth  is  removed, 
and  even  more  than  half  may  be  removed  with  good  effect. 
This  is  especially  true  when  cutting  square  threads  in  brass. 
The  reason  for  this  is  that  when  there  is  little  difference 


§25 


TOOLMAKING. 


39 


in  the  height  of  the  cutting  edges,  they  sometimes  rub  over 
the  surface  of  the  brass  with  a glazing  effect,  making  the 
cutting  more  difficult.  Removing  part  of  the  teeth  reduces 
the  cutting  surface  and  permits  the  others  to  do  more 
effective  service. 


TOOLMAKING. 

(PART  a.> 


CUTTING  TOOLS  AND  APPLIANCES. 


DIES  FOR  THREAD  CUTTING. 


CUTTING  EDGES. 

1.  Number  of  Cutting  Edges. — It  is  now  the  uni- 
versal practice  to  give  dies  four  cutting  edges  for  all 
sizes  up  to  and  including  4 inches.  Beyond  that  size,  prac- 
tice varies.  Some  toolmakers  advocate  five  cutting  edges 
for  dies  above  4 inches;  others  prefer  four  cutting  edges  for 
all  sizes.  There  is  no  particular  objection  to  making  large 
dies  with  five  or  more  cutting  edges  beyond  the  fact  that  it 
slightly  increases  the  first  cost. 

It  is  generally  admitted  that  the  only  instance  in  which  it 
is  absolutely  necessary  to  give  more  than  four  cutting  edges 
to  a thread-cutting  die  is  that  in  which  part  of  the  circum- 
ference of  the  work  to  be  threaded  is  cut  away.  More  cut- 
ting edges  are  then  needed  in  order  to  steady  the  die  and 
thus  prevent  crowding  into  the  work  on  the  side  where  the 
metal  is  cut  away.  The  number  of  cutting  edges  may  then 
be  as  given  in  the  following  table: 

§26 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


TOOLMAKING. 


§26 


TABLE  OF  CUTTING  EDGES  FOR 
SCREW-CUTTING  DIES. 


Circumference  Cut  Away. 

Cutting  Edges. 

none 

4 

is 

5 

tV 

6 

i 

7 

8 

When  more  than  one-sixth  of  the  circumference  is  cut 
away,  dies  usually  will  fail  to  cut  a satisfactory  thread. 

Attention  is  called  to  the  fact  that  it  is  customary  to 
denote  the  size  of  a die  by  the  diameter  of  the  screw  it  will 
cut;  thus,  a die  that  will  cut  a l|--inch  screw  is  called  a 
1^-inch  die,  irrespective  of  the  outside  diameter  of  the  die 
itself. 


2.  Rake  of  Cutting  Edges. — For  general  work  and 
for  dies  that  are  to  be  used  indiscriminately  for  iron,  steel, 
brass  and  other  copper  alloys,  it  is  advisable  to  make  the 
cutting  edges  radial.  For  dies  that  are  to  be  used  entirely 
for  brass  castings,  the  cutting  edge  may  recede  some  from 
a radial  line,  thus  giving  a slight  negative  rake. 


NON- AD  JUST  ABLE  DIES. 

3.  Making  a Solid  Die. — Owing  to  the  difficulty  of 
sharpening  the  cutting  edges,  and  also  owing  to  the  diffi- 
culty of  making  them  to  an  accurate  size,  solid  dies,  i.  e., 
dies  made  out  of  one  piece,  are  used  comparatively  little 
nowadays  in  machine-shop  work.  Being  inexpensive  in 
comparison  with  adjustable  dies,  they  may  sometimes  be 
used  with  advantage  for  special  work  when  only  compara- 
tively few  threads  are  to  be  cut  and  no  great  accuracy  as  to 
size  is  required. 

When  only  one  die  of  a special  size  or  pitch  of  thread  is  to 
be  made,  it  will  scarcely  pay  to  make  a hob  for  cutting  the 


§26 


TOOLMAKING. 


3 


thread  in  it.  The  usual  way,  which  is  also  the  cheapest,  is 
to  cut  the  thread  in  the  lathe,  provided  of  course  the  die  is 
large  enough  to  permit  this  to  be  done.  Since  it  is  very 
difficult  to  measure  an  internal  thread,  a male  thread  gauge 
of  the  required  diameter  and  pitch  of  thread  is  first  made, 
unless  a tap  is  in  existence  that  will  serve  as  a male  gauge. 
The  thread  having  been  cut,  the  beginning  of  the  thread  in 
the  die  is  chamfered  while  still  in  the  chuck.  Cutting  edges 
and  clearance  spaces  are  then  produced  by  drilling  and  filing, 
and,  after  relieving  the  chamfered  threads,  the  die  is  ready 
for  hardening. 

The  die  may  be  made  as  shown  in  Fig.  1.  The  die  illus- 
trated is  round,  being  intended  for  use  in  the  die  holder  of 
a screw  machine.  It  may  be  made  of  any  other  form,  how- 
ever. The  outside  diameter  of  a solid  die  is  usually  fixed 
by  the  diameter  of  the  holder  that  it  is  intended  for,  but 
should  not  be  made  less  than  2.5  times  the  diameter  of  the 


screw  it  is  to  cut.  The  depth  a of  the  die  may  be  1.25  times 
the  diameter  of  the  screw,  and  slightly  more  for  very  small 
screws,  such  as  machine  screws.  If  four  cutting  edges  are 
used,  the  clearance  holes,  as  b , b}  should  be  spaced  equidis- 
tant and  with  their  centers  on  a circle  having  a diameter 
equal  to  the  diameter  of  the  screw  to  be  cut.  The  diame- 
ter c of  the  clearance  holes  is  usually  made  one-half  the  size 


4 


TOOLMAKING. 


§26 


of  the  die,  and  the  top  d of  the  lands  about  one-twentieth 
the  circumference  of  the  circle  tangent  to  the  lands.  The 
cutting  end  of  the  die  is  to  be  chamfered  out  about  three  to 
four  threads  deep,  as  shown  in  the  cross-section.  The  cham- 
fered parts  must  be  relieved  in  order  to  give  keen  cutting 
edges. 

4.  When  making  a solid  die,  cut  the  thread  first.  Then 
screw  in  a piece  of  steel  the  full  length  of  the  die  and  face  it 
off  flush  with  the  faces  of  the  die.  The  temporary  male 
thread  gauge  previously  mentioned  may  be  used  for  this 
purpose  to  advantage  when  only  one  special  size  die  is  to  be 
made.  Lay  out  the  centers  of  the  clearance  holes  on  the 
back  face  of  the  die  and  drill  through.  After  drilling  the 
first  hole,  insert  a plug  that  fits  tightly  into  the  clearance 
hole  just  drilled,  in  order  to  prevent  the  screw  within  the 
die  from  turning  while  drilling  the  other  clearance  holes. 
After  drilling,  remove  the  screw  and  finish  the  back  edge  of 
the  lands  by  filing.  File  the  front  edge  carefully  with  a fine 
file  to  remove  the  burrs,  relieve  the  chamfered  parts,  then 
harden  and  temper,  drawing  to  a good  straw  color. 

5.  When  a large  number  of  solid  dies  of  the  same  size 
are  to  be  made,  it  is  cheaper  to  cut  the  thread  by  tapping, 
finishing  with  a hob  of  correct  size.  The  chamfering  should 
be  done  with  a suitable  taper  reamer  prior  to  tapping.  The 
clearance  holes  may  then  be  drilled  in  a jig;  with  a substan- 
tial jig,  if  the  drilling  is  carefully  done,  there  will  be  no 
need  of  inserting  a screw  in  the  tapped  hole.  The  holes  in 
the  jig  will  steady  the  drill  sufficiently  for  drilling.  For 
rapid  finishing  of  the  clearance  spaces,  a hardened  filing  jig 
will  be  found  of  great  service.  The  relieving  of  the  cham- 
fered cutting  edges  is  usually  done  by  hand.  While  it  can  be 
done  by  special  tools,  this  will  rarely  pay  except  when  the 
number  of  dies  is  very  large. 

6.  Inserted-Blade  Dies. — When  dies  are  required 
for  screws  larger  than  2-inch,  it  is  usually  advisable  to 
make  them  with  blades  inserted  in  a ring  made  of  cast 
iron,  wrought  iron,  or  machinery  steel.  There  are  several 


§26 


TOOLMAKING. 


5 


benefits  gained  by  tnis  construction.  In  the  first  place,  it 
obviates  all  danger  of  losing  the  die  by  cracking  while  hard- 
ening; in  the  second  place,  it  allows  the  die  to  be  readily 
sharpened,  since  the  blades  are  removable  ; and,  again, 
after  the  ring  or  die  body  is  once  made,  new  blades  can  be 
made  at  a fraction  of  the  cost  of  a solid  die.  The  first  cost 
of  an  inserted-blade  solid  die  of  small  size  is  probably  a little 
higher  than  that  of  a solid  die  up  to  2£  inches  in  diameter; 
above  this  size,  the  inserted-blade  solid  die  is  usually  cheaper 
to  construct  and  will  give  better  satisfaction  on  account  of 
ease  of  sharpening  and  repair. 

7.  A very  solid  and  simple  inserted-blade  solid  die  is 
shown  in  Fig.  2.  Dovetailed  slots,  with  the  sides  radial,  are 


^vvVVWVVVS 


Fig.  2. 


planed  in  a ring  of  suitable  inexpensive  material  and  dove- 
tailed blades  are  well  fitted  to  the  slots,  being  made  a 
driving  fit  therein.  The  blades  are  then  faced  flush  with  the 
sides  of  the  holder  ; the  thread  is  now  cut  in  the  lathe, 
the  beginning  of  the  thread  chamfered  off  for  three  to  four 
threads,  as  shown  in  the  partial  cross-section,  and  the 
blades,  after  being  properly  marked,  are  driven  out.  They 
are  then  relieved  on  the  chamfered  part,  hardened,  tem- 
pered, and  driven  home  again  in  their  proper  places  as 
marked. 

For  dies  larger  than  2-inch,  the  following  proportions 
will  serve  as  a guide,  where  d—  diameter  of  screw  ; outside 


6 


TOOLMAKING. 


§26 


diameter  of  die  body  = 2.4  to  2.5  d ; inside  diameter  of  die 
body  =1.3- <2^;  length  of  blade  =1.25  d ; width  of  lands, 
when  four  blades  are  used,  as  is  recommended  for  general 
work,  about  one-sixteenth  the  circumference  of  the  screw 
to  be  cut.  When  more  blades  are  used,  the  lands  must 
be  made  narrower.  If  the  nature  of  the  work  demands  it, 
the  blades  of  an  inserted-blade  die  may  project  somewhat 
beyond  the  faces  of  the  die  body.  They  should  not  project 
more  than  the  width  of  the  lands,  however;  otherwise  they 
are  liable  to  break  off  under  the  strain  of  cutting. 


ADJUSTABLE  DIES. 

8.  There  is  a great  variety  of  adjustable  dies  made 
for  general  work.  Since  special  sizes  of  these,  for  use  in  the 
ordinary  die  stocks,  can  be  obtained  of  the  makers  for  less 
than  they  can  generally  be  made  in  the  tool  room,  the  tool- 
maker  is  rarely  called  on  to  make  them.  If  such  should 
be  the  case,  there  are  generally  dies  at  hand  that  will  serve 
as  a guide  in  making  a special  die. 

9.  Spring  Die.  — In  many  cases  spring  dies  for  screw- 
machine  work  are,  for  various  reasons,  made  in  the  tool  room, 
although,  generally  speaking,  they  may  be  bought  more 
cheaply  from  concerns  making  a specialty  of  taps  and  dies. 

These  dies  are  always  used  with  a clamp  col- 
lar that  serves  to  adjust  them.  When  a 
spring  die  is  to  be  made,  it  is  good  practice  to 
fit  it  to  one  of  the  clamp  collars  at  hand,  thus 
saving  the  expense  of  making  a new  clamp 
collar.  Provide  four  cutting  edges  for  gen- 
eral work,  making  the  lands  about  one-six- 
teenth the  circumference.  Chamfer  about 
three  to  three  and  one-half  threads  and  re- 
lieve to  give  keen  cutting  edges.  The  depth 
of  the  thread  may  be  about  one  and  one- 
quarter  times  the  diameter  of  the  screw  to  be  cut.  For  the 
cutting  edges,  use  a 45°  milling  cutter  that  will  split  the  die 
as  shown  in  Fig.  3.  Tap  the  die  with  a hob  the  same  size  as 


26 


TOOLMAKING. 


7 


the  screw  to  be  cut.  After  splitting  the  die,  the  burrs 
thrown  up  on  the  threads  may  be  removed  by  running  the 
hob  through  again.  Finish  the  cutting  edges  by  filing  with 
a fine  file,  stamp  the  size  and  the  number  of  threads  on  the 
die,  and  then  harden  as  far  as  the  end  of  the  thread  and 
temper  to  a deep  straw  color. 

For  accurate  uniform  threads,  two  dies  must  be  used,  one 
for  roughing  out  and  the  other  for  the  finishing  cut.  To  do 
good  work,  the  cutting  edges  must  be  kept  sharp;  dies 
made  as  shown  in  Fig.  3 can  readily  be  sharpened  by  grind- 
ing the  face  of  the  lands  on  a suitable  emery  wheel. 

lO.  Average  proportions  of  spring  dies  are  given  in  the 
following  table,  where  all  dimensions  are  given  in  inches. 
It  is  to  be  understood  that  the  proportions  given  are  in- 
tended only  as  a guide,  and,  hence,  may  be  departed  from 
to  some  extent  to  suit  special  requirements. 

TABLE  OF  SPRING-DIE  PROPORTIONS. 


Size  of  Screw. 

Outside  Diameter. 

Length. 

i to  ¥ 

i 

ito  f 

i 

if 

t to  \ 

l 

2 

ito  t 

li 

H 

f to  1 

If 

2} 

1 to  li 

2 

3 

li  to  1^- 

H 

H 

H to  if 

H 

4 

If  to  2 

H 

When  spring  dies  are  to  be  used  for  work  whose  circum- 
ference is  partly  cut  away,  make  the  number  of  cutting 
edges  as  given  in  the  table  of  Art.  1.  A cutter  to  suit  the 
increased  number  of  cutting  edges  will  then  have  to  be  se- 
lected for  slitting  the  die.  The  spring  die  is  probably  the 
cheapest  adjustable  die  for  screw-machine  and  turret-lathe 
work  up  to  and  including  2 inches  in  diameter,  as  far  as 


C.  6*.  III.-v 


8 


TOOLMAKING. 


§26 


first  cost  is  concerned.  When  threads  larger  in  diameter 
are  to  be  cut,  it  is  usually  more  economical  to  use  some  form 
of  adjustable  die  with  inserted  blades. 

11.  Inserted-Blade  Adjustable  Die. — One  of  the 

simplest  designs  of  an  adjustable  die  with  inserted  blades  is 
that  shown  in  Fig.  4.  The  blades  are  inserted  exactly  as  in 


the  die  shown  in  Fig.  2;  the  die  body  is  then  split,  as  shown, 
and  an  adjusting  screw  put  in.  When  this  die  is  used  in  its 
holder,  the  setscrews  of  the  holder  will  lock  the  die  firmly 
together.  Its  only  drawback  is  the  necessity  of  removing 
the  die  from  the  holder  every  time  it  is  desired  to  adjust  it.\ 
This  may  be  overcome,  however,  by  cutting  a hole  through 
the  holder  in  the  proper  place  to  allow  the  adjusting  screw 
to  be  reached  with  a screwdriver.  For  very  large  dies,  two 
adjusting  screws  may  be  provided,  locating  each  near  one 
of  the  faces. 

The  only  thing  that  may  prove  difficult  to  one  that  has 
never  done  this  before  is  the  drilling  and  counterboring  of 
the  hole  for  the  adjusting  screw.  This  job  may  be  done  in 
a jig  if  a large  number  of  dies  are  to  be  made;  in  case  of  a 
limited  number,  it  may  be  done  in  a lathe  or  a milling  ma- 
chine, strapping  the  die  body  to  the  top  of  the  slide  rest 
or  to  the  milling-machine  platen.  Using  a two-lipped  mill- 
ing cutter  of  correct  size,  the  counterbore  can,  by  careful 


26 


TOOLMAKING. 


9 


feeding,  be  cut  without  much  trouble.  Drilling  is  then  done 
while  the  die  body  is  still  strapped  down,  catching  the  drill 
in  a chuck.  If  the  die  body  has  been  split  prior  to  drilling 
the  hole  for  the  adjusting  screw,  an  iron  or  wooden  shim 
should  be  inserted  in  the  slot. 


13IE  HOLDERS. 

12.  For  screw-machine  and  turret-lathe  work,  solid  and 
adjustable  dies  are  inserted  in  releasing  die  holders  made 
on  the  same  principle  as  a releasing  tap-  holder.  The  die 
is  held  in  the  holder  by  three  or  four  pointed  setscrews 
that  enter  conical  depressions,  as  shown  in  Fig.  5.  These 


fig.  5. 


depressions  are  so  located  that  the  tightening  up  of  the  set- 
screws will  draw  the  die  against  the  shoulder  of  the  holder. 
The  length  of  the  die  holder  naturally  depends  on  the  length 
of  the  screw  to  be  cut.  One  or  two  liberal-sized  openings 
should  be  cut  through  the  holder  back  of  the  die,  to  provide 
for  free  escape  of  the  chips.  Practical  considerations  pro- 
hibit the  use  of  the  holder  shown  for  very  long  screws.  For 
these  a releasing  holder  may  be  constructed  in  a somewhat 


10 


TOOLMAKING. 


26 


different  manner,  retaining  the  same  principle  of  releasing 
and  clutching  for  backing  the  die  off. 


13.  A design  for  such  a holder  is  shown  in  Fig.  6.  It 
consists  essentially  of  two  parts,  a shank  a to  fit  the  turret 
and  a die  holder  b.  The  clutching  and  releasing  mechanism 


is  contained  in  the  front  part  of  the  device.  For  releasing, 
two  stop-pins  are  employed;  the  one  is  driven  into  the 
holder  and  the  other  into  the  shank,  as  shown.  The  for- 
ward part  of  the  shank  is  enlarged  and  grooved  to  receive 
the  end  of  the  backing  pin  c,  which  in  the  design  here  illus- 
trated is  firmly  screwed  into  the  holder  proper.  The  for- 
ward side  of  the  cylindrical  groove  forms  a helix  that  serves 
to  guide  the  backing  pin  into  its  place.  The  die  holder 
proper  is  bored  to  be  a good  sliding  fit  on  the  front  end  of 
the  shank.  In  the  position  shown,  the  clutch  pins  are  disen- 
gaged and  the  holder  is  free  to  rotate  about  the  shank.  If 
the  turret  is  now  withdrawn  while  the  work  just  threaded  is 
revolving  in  a reverse  direction,  the  backing  pin  c is  guided 
into  place,  clutches  the  shank,  and  the  die  is  unscrewed  from 
the  work.  The  shank  has  a hole  drilled  through  it  to  admit 
the  threaded  work. 


§26 


TOOLMAKING. 


11 


In  designing  such  a holder,  care  should  be  taken  to  locate 
the  backing  pin  and  the  groove  so  that  the  groove  will  not 
be  uncovered  when  the  backing  pin  clutches  the  shank.  If 
the  die  holder  is  to  be  used  for  a right-hand  die,  the  helical 
side  of  the  groove  must  be  right-handed,  that  is,  as  shown 
in  the  illustration.  For  a left-handed  die,  it  must  be  left- 
handed.  If  desired,  the  device  may  be  adapted  to  both  right- 
handed  and  left-handed  threads.  To  do  this,  the  enlarged 
end  of  the  shank  is  made  long  enough  to  receive  two  grooves ; 
the  front  side  of  one  is  then  made  a right-handed  helix,  and 
the  front  side  of  the  other  a left-handed  helix.  A hole  to 
receive  the*  backing  pin  is  drilled  and  tapped  for  each  groove ; 
the  backing  pin  may  then  be  changed  from  one  groove  to 
the  other.  A blank  screw  should  be  provided  to  fill  the 
backing-pin  hole  not  in  use.  Also  provide  one  or  two  open- 
ings for  the  escape  of  chips.  The  helical  side  of  the  groove 
is  most  conveniently  cut  in  an  engine  lathe  geared  to  the 
correct  pitch,  which  may  be  about  one  and  one-half  times  the 
diameter  of  the  backing  pin. 


REAMERS. 


CLASSIFICATION  OF  REAMERS. 

14.  Reamers  may,  in  accordance  with  their  shape,  be 
divided  into  three  general  classes.  These  are  straight 
reamers,  taper  reamers,  and  formed  reamers.  Each 
of  these  classes  may  be  divided  into  three  subclasses,  in 
accordance  with  their  construction.  These  are  solid  ream- 
ers, inserted-blade  reamers,  and  adjustable  reamers. 

Reamers  are  generally  intended  for  the  production  of 
round  smooth  holes  of  accurate  size.  In  some  cases,  they 
are  merely  intended  to  enlarge  holes  without  particular 
reference  to  the  holes  being  true  and  straight.  Experience 
has  shown  that,  in  order  to  produce  round  and  smooth  holes, 
reamers  must  have  their  cutting  edges  spaced  and  formed 


12 


TOOLMAKING. 


§26 


correctly.  It  must  not  be  inferred  from  this  statement, 
however,  that  there  is  but  one  correct  way  of  spacing  and 
forming  the  cutting  edges;  the  required  result  may  be 
arrived  at  in  various  ways. 


CHATTERING. 

1 5.  Chattering,  which  is  a common  fault  of  reamers, 
is  in  itself  an  evidence  of  incorrect  design  or  construction  of 
the  reamer.  It  is  due  to  several  entirely  preventable 
causes,  any  one  of  which,  when  present  alone  or  in  combi- 
nation with  one  or  more  of  the  others,  will  induce  it. 
Whether  a chattering  reamer  can  be  cured  or  not  depends 
on  its  design  and  construction. 

A knowledge  of  the  causes  that  induce  chattering  of  a 
reamer  will  indicate  whether  it  can  be  cured  or  not.  The 
causes  of  chattering  are  as  follows: 

1.  Equidistant  spacing  of  the  cutting  edges. 

2.  Excessive  front  rake  of  the  cutting  edges. 

3.  Excessive  clearance  of  the  lands. 

If  the  cutting  edges-  are  spaced  equidistant  around  the 
circumference,  each  edge  will  follow  in  the  track  of  the 
others.  Experience  has  shown  that  this  condition  is  not 
conducive  to  the  production  of  a round  hole.  Excessive 
front  rake  will  cause  the  reamer  to  cut  too  freely,  or  “ take 
a greedy -bite,”  as  it  is  called.  This  precludes  the  possibility 
of  producing  a smooth  hole,  since  smoothness  can  be  attained 
more  readily  by  a scraping  cut.  Excessive  clearance,  or 
relief,  of  the  lands  robs  the  reamer  of  the  support  it  should 
derive  from  them;  consequently,  it  works  unsteadily  and 
with  a wobbling  motion. 


SPACING  OF  CUTTING  EDGES. 

16.  Two  different  systems  of  spacing  are  in  general 
use,  either  one  of  which  will  tend  to  prevent  chattering. 
One  system  is  shown  in  Fig.  7.  In  this,  the  cutting  edges 


§26 


TOOLMAKING. 


13 


are  spaced  irregularly  and 
opposite  each  other.  In 
ularity  of  the  spacing,  a 
supplementary  dotted 
circle  has  been  drawn  and 
divided  into  equidistant 
divisions.  Since  no  two 
edges  are  opposite  each 
other,  the  diameter  of  the 
reamer  cannot  be  meas- 
ured by  calipering  and  it 
can  only  be  brought  to 
size  by  fitting  it  to  a ring 
gauge  of  correct  size. 

This  drawback  is  over- 
come in  the  system  of 
spacing  shown  in  Fig.  8. 


no  two  edges  are  diametrically 
order  to  show  clearly  the  irreg- 


Here 


Fig.  7- 

the  spacing  is  so  arranged 
that  any  two  opposite  cut- 
ting edges  are  on  the  same 
diameter.  Hence,  the 
reamer  can  be  calipered, 
and,  for  this  reason,  the 
general  adoption  of  this 
system  of  spacing  is 
recommended.  While 
Figs.  7 and  8 show  a sec- 
tion of  a solid  reamer,  the 
methods  of  spacing  shown 
apply  to  inserted-blade  and 
adjustable  reamers  as  well. 


NUMBER  OF  CUTTING  EDGES. 

17.  Fluted  reamers  for  lathe  and  handwork,  with  the 
exception  of  rose  reamers  and  special  reamers  designed  to 
rapidly  remove  a relatively  large  amount  of  metal,  are  rarely 
given  less  than  six  cutting  edges.  For  solid  reamers,  the  num- 
ber of  cutting  edges  may  be  as  given  in  the  following  table: 


14 


TOOLMAKING. 


§26 


TABLE  OF  CUTTING  EDGES  FOR  REAMERS. 


Diameter  of  Reamer. 

Cutting  Edges. 

i to  i 

G 

i to  1 

8 

1 to  H 

10 

li  to  2± 

12 

2J  to  3 

14 

Generally  speaking,  there  is  nothing  to  be  gained  by 
giving  a larger  number  of  cutting  edges  than  that  given  in 
the  table. 

18.  In  inserted-blade  reamers,  the  largest  number  of 
cutting  edges  that  can  be  given  depends  on  the  thickness  of 
the  blades.  They  are  usually  made  with  less  cutting  edges 
than  solid  reamers.  It  was  believed  formerly,  and  the 
view  is  still  held  by  many,  that  a reamer  must  have  an  odd 
number  of  cutting  edges  in  order  to  work  well.  Actual 
experience  with  properly  formed  reamers  has  demonstrated 
conclusively  that,  as  far  as  truth,  ease  of  working,  and 
smoothness  are  concerned,  it  does  not  make  the  slightest 
difference  whether  the  number  of  cutting  edges  is  odd  or 
even.  On  account  of  being  able  to  caliper  the  reamer,  an 
even  number  of  cutting  edges  is  really  preferable.  Rose 
reamers  may  be  given  from  three  to  seven  flutes,  according 
to  size.  In  the  small  sizes,  they  may  be  made  without  any 
teeth  between  the  flutes,  and,  in  the  large  sizes,  may  have 
one  or  two  teeth  between  each  flute. 


FLUTING. 

19.  A form  of  flute  that  is  very  satisfactory  is  that 
shown  in  Figs.  7 and  8.  This  form  of  flute  leaves  the 
reamer  very  strong  and,  at  the  same  time,  by  the  absence 
of  a sharp  corner,  reduces  the  possibility  of  the  reamer 
cracking  in  the  corner  of  the  flutes  in  hardening.  Another 


§26 


TOOLMAKING. 


15 


good  form  of  flute  is  that  recommended  by  Brown  & 
Sharpe,  which  is  shown  in  Fig.  9.  This  form  gives  a 
greater  clearance  space 
than  the  flute  with  sides 
at  right  angles  to  each 
other.  Milling-machine 
cutters  for  this  form  of 
flute  may  be  obtained 
from  the  Brown  & Sharpe 
Manufacturing  Company. 

These  cutters  are  to  be  set 
so  as  to  give  a slight  nega- 
tive rake  to  the  cutting 
edge.  To  allow  the  nega- 
tive rake  to  be  seen  plainly, 
two  dotted  diameters  have 
been  drawn  in  Fig.  9.  When  using  this  form  of  flute,  the  cut- 
ter must  be  set  to  such  a depth  that  the  land  will  be  about 
one-fifth  the  average  distance  from  one  cutting  edge  to  the 
next.  If  the  flute  is  cut  deeper,  the  cutting  edges  become 
too  springy  for  good  work.  When  flutes  of  the  form  shown 
in  Figs.  7 and  8 are  used,  the  lands  may  be  about  one-eighth 
the  average  distance  from  one  cutting  edge  to  the  next. 

In  general,  a reamer  will  work  more  smoothly  if  the 
cutting  edge  is  given  a slight  negative  rake,  since  it  will 
then  take  a scraping  cut.  The  amount  of  negative  rake 
need  not  exceed  that  shown  in  Fig.  9,  which  is  about  5°. 
If  the  reamer  is  to  be  used  entirely  for  steel,  the  cutting 
edges  may  be  radial,  like  in  Figs.  7 and  8. 


CLEARANCE. 

20.  In  order  that  the  reamer  may  cut  freely,  the  lands 
must  be  relieved  back  of  the  cutting  edge.  This  relief  can 
be  given  either  by  grinding  the  reamer  with  an  emery  wheel 
in  a suitable  fixture,  or  by  oilstoning.  The  amount  of 
clearance  to  be  given  depends  on  the  purpose  of  the  reamer. 
If  it  is  to  be  used  for  roughing  out,  the  clearance  should  be 


16 


TOOLMAKING. 


§26 

more  than  is  given  to  a finishing  reamer.  It  should  be 
least  for  a finishing  reamer  that  is  intended  to  keep  its  size 
for  a long  time.  Fig.  10  shows  the  appearance  of  reamer 
teeth  properly  relieved  for  different  purposes. 

In  Fig.  10  ( a ),  the  relief  to  be  given  to  a roughing  reamer 
is  shown.  If  the  lands  are  thus  relieved,  the  reamer  will 


Fig.  io. 


cut  freely,  but  cannot  be  expected  to  make  as  true  a hole 
or  last  as  long  as  the  reamer  having  its  teeth  relieved  as 
shown  in  Fig.  10  ( b ).  This  latter  form  of  relief  leaves  the 
cutting  edge  better  supported,  and,  consequently,  the  reamer 
will  work  more  smoothly  and  keep  its  size  longer  than  with 
the  form  first  shown.  It  will  not  cut  as  freely,  however. 
Fig.  10  (c)  shows  the  form  of  clearance  to  be  adopted  when 
it  is  important  to  reduce  the  wear  of  the  reamer  to  a mini- 
mum in  order  to  produce  a large  number  of  holes  of  the  same 
size.  As  shown,  the  land  is  backed  off  on  the  arc  of  a circle. 
The  amount  of  clearance  at  the  back  edge  is  made  the  same 
as  in  Fig.  10  ( b ),  but,  owing  to  the  circular  form  of  the 
relief,  the  cutting  edge  is  supported  better.  If  desired, 
roughing  reamers  may  be  backed  off  on  the  arc  of  a circle; 
however,  this  is  more  expensive  than  the  flat  backing  off 
shown. 

The  amount  that  the  back  edge  of  the  land  should  clear 
cannot  be  definitely  expressed  by  any  simple  rule,  since  it 


§26 


TOOLMAKING. 


17 


depends  on  several  variable  factors.  As  an  aid  in  deciding 
what  clearance  to  give,  it  may  be  stated  that,  for  a roughing 
reamer,  the  angle  b , see  Fig.  10,  may  be  about  80°.  For  a 
finishing  reamer,  the  angle  b may  be  from  85°  to  88°,  using 
the  smaller  angle  for  brass,  which,  in  general,  requires  more 
clearance. 


HELICAL  CUTTING  EDGES. 

21.  In  order  to  prevent  a reamer  from  drawing  into  the 
work,  the  cutting  edges  may  be  cut  helically,  choosing  a 
left-handed  helix  for  a straight  reamer  that  is  to  turn  right- 
handed.  The  helix  should  be  such  that  the  cutting  edges 
will  make  an  angle  of  about  15°  with  a plane  passing  through 
the  axis  of  the  reamer.  Right-handed  helical  cutting  edges 
are  of  advantage  for  taper  reamers  having  a very  coarse 
taper,  and  for  formed  reamers  that  differ  considerably  in 
their  various  diameters,  as  it  will  assist  them  to  cut.  Fin- 
ishing taper  reamers  and  finishing  formed  reamers  may  have 
their  cutting  edges  left-handed,  if  made  helical.  Some  tool- 
makers  claim  that  if  thus  formed,  owing  to  the  shaving  cut 
taken,  they  will  produce  a smoother  and  truer  hole  than  can 
be  obtained  otherwise. 

The  advantages  of  helical  cutting  edges  for  straight 
reamers  are  somewhat  doubtful,  at  least  for  general  work; 
many  toolmakers  believe  that  the  extra  expense  involved  in 
making  them  is  not  justified  by  the  results,  claiming  that, 
with  reasonable  care,  just  as  true  and  smooth  a straight  hole 
can  be  obtained  with  a reamer  having  its  cutting  edges 
straight.  Helical  cutting  edges  for  straight  reamers  are 
recommended  when  holes  are  to  be  reamed  that  are  pierced 
crosswise  by  openings.  All  remarks  previously  made  in 
regard  to  spacing,  number,  and  clearance  of  cutting  edges 
apply  to  helical  cutting  edges  as  well. 


ALLOWANCE  FOR  GRINDING. 

22.  Since  there  is  no  way  of  preventing  a reamer  from 
warping  in  hardening,  an  allowance  must  be  made  to  allow 
it  to  be  finished  by  grinding.  The  amount  to  be  allowed 


18 


TOOLMAKING. 


§26 


for  grinding  depends  on  the  length  and  diameter  of  the 
reamer;  it  is  least  for  a short  and  most  for  a long  reamer. 
For  reamers  up  to  f-  inch,  and  not  over  6 inches  long,  ex- 
clusive of  shank,  an  allowance  of  .025  inch  will  usually  prove 
ample,  since  there  is  no  particular  difficulty  in  straightening 
the  reamer  sufficiently  to  allow  it  to  be  trued  with  this 
allowance.  For  every  \ inch  the  reamer  is  above  this  size, 
the  allowance  may  be  increased  .01  inch,  provided  the  reamer 
is  not  over  8 diameters  long.  If  longer,  the  allowance  for 
grinding  should  be  increased. 


GRINDING  REAMERS. 

2> 3.  For  grinding  reamers,  a grinding  machine  is 
most  convenient,  although  straight  and  taper  reamers  can 
be  ground  true  by  other  means  if  the  shop  has  no  grinding 


machine  or  grinding  fixture  for  converting  a lathe  tem- 
porarily into  a grinding  machine.  The  reamer  should  first 
be  ground  to  run  true,  revolving  it  between  the  centers.  It 


§26 


TOOLMAKING. 


19 


may  be  ground,  according  to  its  size,  to  within  xgVrr  or  t ttW 
inch  of  the  finished  size.  The  clearance  is  then  ground  with 
the  emery  wheel  so  set  that  its  periphery  will  clear  the  front 
edge  of  the  tooth  succeeding  the  one  being  ground.  The 
reamer  is  kept  from  rotating  by  a finger  so  adjusted  that 
the  correct  clearance  will  be  ground.  The  relative  position 
of  emery  wheel,  reamer,  and  guiding  finger  is  shown  in 
Fig.  11.  The  guiding  finger  a is  fastened  right  in  front  of 
the  wheel  to  the  carriage  that  carries  the  emery  wheel  and 
travels  along  with  it,  thus  always  supporting  the  reamer 
tooth  directly  at  the  point  where  the  wheel  is  cutting.  The 
emery  wheel  should  always  rotate  in  such  a direction  that 
in  grinding  it  tends  to  press  the  reamer  tooth  down  on 
the  finger,  thus  preventing  rotation  of  the  reamer  during 
grinding. 

The  arrow  x shows  the  correct  direction  of  rotation  of  the 
emery  wheel.  As  shown  in  the  figure,  the  height  of  the 
finger  is  so  adjusted  that  the  cutting  edge  is  below  the  line 
joining  the  centers  of  the  reamer  and  emery  wheel.  The 
farther  the  cutting  edge  is  placed  below  the  center  line,  the 
greater  the  clearance  produced  by  the  wheel;  conversely, 
the  nearer  to  the  center  line,  the  less  the  clearance.  From 
this,  it  is  seen  that  varying  amounts  of  clearance  can  be 
obtained  with  the  same  wheel  and  on  the  same  reamer  by 
varying  the  height  of  the  finger. 

24.  In  grinding  the  clearance,  the  metal  must  be  re- 
moved by  a succession  of  light  cuts,  going  successively 
around  the  reamer.  It  is  of  the  utmost  importance  that  the 
temper  of  the  cutting  edge  should  be  preserved  ; a heavy  cut 
taken  with  a dry  emery  wheel  is  almost  certain  to  anneal 
the  cutting  edge,  thus  rendering  the  reamer  worthless. 
The  clearance  must  not  be  ground  up  to  the  cutting  edge; 
according  to  the  size  of  the  reamer,  it  may  be  ground  to 
within  from  .01  to  .02  inch  of  the  edge.  The  reamer  is  then 
brought  to  a sharp  edge  and  to  correct  size  by  oilstoning. 
For  grinding  the  clearance,  as  large  an  emery  wheel  as  the 
machine  will  handle  should  be  used,  since  the  larger  the 


20 


TOOLMAKING. 


§26 


wheel,  the  less  concave  the  clearance  will  be.  A small 
wheel  will  grind  the  clearance  so  hollow  that  the  cutting 
edge  will  be  deprived  of  support. 

25.  If  no  grinding  machine  or  fixture  is  available,  a 
straight  or  taper  reamer  may  be  ground  in  a lathe  to  run  true. 
A piece  of  free-cutting  oilstone,  preferably  of  Washita  stone, 
is  held  in  the  tool  post.  The  reamer  is  revolved  backwards 
at  a high  speed  and  the  oilstone  brought  up  by  means  of  the 
cross  feed-screw  until  it  slightly  engages  the  reamer.  The 
carriage  is  then  rapidly  moved  back  and  forth  by  hand  ; if 
freely  lubricated,  the  oilstone  will  gradually  cut  the  reamer 
down  until  it  is  round  and  true.  Clearance  is  given  entirely 
by  oilstoning  at  a right  angle  to  the  axis  of  the  reamer. 
The  method  here  given  is  naturally  very  slow  and  expensive 
and  is  to  be  recommended  only  as  a makeshift.  It  is  doubt- 
ful whether  a reamer  can  be  made  as  round  and  true  by  it 
as  can  be  done  by  a grinding  machine,  or  by  means  of  a 
proper  grinding  fixture. 


GROOVING  REAMERS. 

26.  A reamer  can  be  grooved  most  rapidly  in  a milling 
machine  with  a suitable  cutter.  As  a makeshift,  the  grooves 
can  be  planed  in  the  lathe,  shaper,  or  planer.  This  is  not 
recommended,  however,  except  when  no  milling  machine  is 
available. 

Suppose  the  method  of  spacing  in  which  any  two  opposite 
teeth  are  on  the  same  diameter  has  been  selected.  Then,  the 
grooves  are  most  advantageously  cut  in  pairs;  that  is,  after 
milling  one  groove,  the  one  diametrically  opposite  is  cut 
before  passing  to  the  adjoining  one.  This  is  recommended 
on  account  of  the  saving  in  labor  accomplished  by  it.  In  the 
method  of  spacing  selected,  any  two  opposite  grooves  will 
have  the  same  depth,  and  any  two  adjoining  grooves  will 
differ  in  depth.  Consequently,  by  adopting  the  method  of 
cutting  the  grooves  in  pairs,  the  number  of  times  the  cutter 
must  be  reset  is  reduced  to  one-half  of  what  it  would  be 
when  cutting  one  groove  after  another. 


§26 


TOOLMAKING. 


21 


27.  The  irregularity  of  spacing  is  obtained  by  moving 
the  index  pin  a different  number  of  holes  for  each  adjoining 
pair  of  grooves.  The  irregularity  introduced  need  not  be 
very  large;  one  that  will  cause  the  cutting  edge  to  diverge 
by  2°  to  4°  from  the  angle  corresponding  to  an  equal  divi- 
sion will  be  sufficient. 

An  example  will  show  how  the  irregularity  is  introduced. 
Suppose  we  wish  to  cut  a reamer  with  8 cutting  edges, 
and  that  the  milling  machine  available  requires  40  turns  of 
the  index  pin  for  one  revolution  of  the  index-head  spindle. 
Then,  with  the  index  pin  adjusted  to  the  circle  having  20 
holes,  20  X 40  = 800  holes  must  be  passed  over  for  a complete 
revolution  of  the  reamer,  and  800  -f8  = 100  holes  for  dividing 
into  eight  equal  divisions.  As  a movement  of  800  holes 
causes  the  work  to  revolve  through  360°,  the  angle  through 
which  it  is  revolved  by  a movement  of  1 hole  is  = say  -j-°, 
or  .5°. 


If  we  wish  to  introduce  an  irregularity  of  2°,  it  needs  a 


2 

movement  of  — = 4 holes. 


Then,  by  a judicious  selection, 


we  arrange  the  number  of  holes  to  be  passed  over  for  each 
division.  For  instance,  we  may  use  successively  95,  99,  105, 
and  101  holes  for  adjoining  grooves,  and,  after  cutting  each 
groove,  give  20  turns  to  pass  to  the  opposite  one.  With  this 
number,  the  greatest  difference  between  adjoining  gooves 
is  that  corresponding  to  101  — 95  = 6 holes,  which  is  about 
6 X i = 3°.  If  the  number  of  holes  selected  for  successive 
grooves  had  been  98,  102,  106,  and  94,  the  greatest  difference 
between  adjoining  holes  would  have  been  that  correspond- 
ing to  106  — 94  = 12  holes;  or  12  X y — 6°.  In  selecting  the 
holes,  it  must  be  remembered  that  the  sum  of  the  holes 
must  be  equal  to  one-half  the  number  of  holes  required 
for  a whole  revolution  of  the  reamer.  Consequently,  the 
number  of  holes  required  for  the  last  groove  is  equal  to  the 
difference  between  the  sum  of  the  preceding  ones  and  the 
number  of  holes  required  for  one-half  of  a revolution  of  the 
work. 

The  moves  that  are  to  be  made  successively  in  order  tQ 


22 


TOOLMAKING. 


26 


obtain  the  spacing  are  as  follows  for  the  particular  division 
and  spacing  selected:  Referring  to  Fig.  12,  to  cut  the  first 
groove,  none;  to  cut  the  fifth  groove,  20  complete  turns  of 
the  index  pin;  to  cut  the  fourth  groove, 
95  holes,  or  4 turns  and  15  holes;  to  cut 
the  eighth  groove,  20  complete  turns;  to 
cut  the  seventh  groove,  99  holes,  or  4 
turns  and  19  holes ; to  cut  the  third  groove, 
20  complete  turns  ; to  cut  the  second 
groove,  103  holes,  or  5 turns  and  3 holes; 
and  to  cut  the  sixth  groove,  20  complete 
turns.  A movement  of  101  holes,  or  5 turns  and  1 hole,  will 
bring  the  cutter  to  the  fifth  groove  again,  and  20  complete 
turns  to  the  first  groove. 

When  making  a solid  reamer,  it  is  necessary  to  go  around 
twice,  sinking  the  cutter  in  deep  enough  the  first  time  to 
distinctly  mark  the  position  of  the  cutting  edge.  When 
back  to  the  first  groove,  the  cutter  may  be  sunk  deep  enough 
to  give  the  proper  width  of  land,  which  can  be  determined 
readily  if  the  position  of  the  cutting  edge  of  the  adjoining 
groove  is  known.  Then,  after  cutting  grooves  1 and  5,  the 
cutter  must  be  reset  to  the  proper  depth  for  grooves  ^ and 
8 , 7 and  3,  and,  finally,  2 and  6.  If  the  grooves  are  helical, 
the  spacing  is  obtained  in  just  the  same  manner. 

28.  It  must  not  be  inferred  that  it  is  necessary  to  use 
the  20-hole  circle  for  an  8-grooved  reamer,  or  that  the  num- 
ber of  holes  passed  over  for  each  division  must  be  just  as 
given  in  the  preceding  discussion.  The  numbers  of  holes 
and  the  20-hole  circle  have  been  arbitrarily  selected  in  order 
to  illustrate  the  principle  involved. 


TEMPER  OF  REAMERS. 

29.  The  cutting  edges  of  a reamer  may  be  tempered  to 
suit  the  service  to  be  performed.  When  the  reamer  is  to 
remove  a relatively  large  amount  of  metal  in  one  operation, 
the  cutting  edges  should  be  soft  and  tough  enough  to  stand 


TOOLMAKING. 


23 


§ 26 

the  strain  of  cutting;  when  a reamer  is  intended  for  finish- 
ing and  accurate  sizing  of  holes,  where  it  has  to  remove  only 
a very  small  amount  of  metal,  it  can  advantageously  be 
made  quite  hard.  A roughing  reamer,  after  being  hardened 
so  that  a file  will  not  touch  it,  may  be  drawn  to  a full 
straw  color,  while  a finishing  reamer  may  be  left  a pale  straw 
color.  If  the  finishing  reamer  is  intended  for  very  light 
service,  and  if  it  is  essential  that  the  wear  of  the  reamer  be 
reduced  to  its  lowest  limit  in  order  to  make  a large  number 
of  holes  uniform  in  size,  it  may  even  be  left  as  hard  as  fire 
and  water  can  make  it,  provided,  of  course,  that  the  steel 
is  not  heated  hot  enough  to  burn  it. 


TAPER  REAMERS. 

30.  If  intended  for  finishing,  taper  reamers  are  made 
on  the  same  principles  that  govern  the  construction  of 
straight  reamers.  Roughing  taper  reamers  are  often  made 
in  the  same  manner,  but  with  right-handed  helical  cutting 
edges.  If  the  taper  of  the  reamer  is  at  all  large,  the  rough- 
ing reamer  may  be  made  as  shown  in  Fig.  13.  This  con- 


FlG.  13. 


struction  is  an  extension  of  the  principle  on  which  a counter- 
bore is  based;  in  fact,  each  step  in  conjunction  with  the 
adjoining  one  forms  a counterbore.  All  cutting  is  done  at 
the  forward  end  of  the  steps;  the  cutting  edges,  as  a , a , are 
formed  by  backing  off  with  a file.  The  parts  of  the  cylin- 
drical surface  of  each  step,  which  remain  after  the  grooves 
are  cut,  are  left  cylindrical;  no  clearance  is  given,  as  they 
serve  the  purpose  of  guiding  the  succeeding  cutting  edges. 


C.  S . 111.-32 


24 


TOOLMAKING. 


§ 20 


The  reamer  may  be  given  four  cutting  edges,  which  may 
be  cut  with  a milling  cutter  suitable  for  a tap  of  the  same 
size. 

If  the  reamer  is  to  be  used  for  brass  or  cast  iron,  the  flutes 
may  be  made  straight,  as  shown  in  the  figure;  if  it  is  to  be 
used  for  roughing  wrought  iron  and  steel,  the  flutes  may  be 
helical,  using  a right-handed  helix  of  such  a pitch  that  it  will 
make  an  angle  of  about  15°  with  a plane  passing  through  the 
axis.  The  reamer  being  intended  to  turn  right-handed,  the 
cutting  of  right-handed  helical  flutes  has  the  effect  of  giving 
keen  cutting  edges,  which  will  make  the  reamer  work  easily; 
at  the  same  time,  the  chips  are  crowded  back  toward  the 
shank.  When  turning  up  a stepped  reamer,  it  is  advisable 
to  neck  it  down  a little  with  a round-nosed  tool  at  the  end  of 
each  step.  When  grinding,  the  grooves  allow  the  grinding 
wheel  to  pass  entirely  over  the  surfaces,  and,  furthermore, 
they  make  it  easier  to  sharpen  the  cutting  edges.  The  cut- 
ting edges  are  backed  off  by  filing  before  hardening;  when 
grinding  the  steps,  the  extremity  of  the  cutting  edges  of 
each  step  can  be  trued  at  the  same  time,  removing  as  little 
metal  as  possible.  They  are  finally  brought  to  a sharp  edge 
again  by  careful  hand  grinding  on  a beveled  emery  wheel, 
or  by  oilstoning. 

Stepped  reamers  may  also  be  made  of  suitable  form  to 
rough  out  holes  that  are  to  be  finished  with  formed  reamers. 
The  number  of  steps  that  are  to  be  used  for  a stepped  reamer 
must  be  decided  separately  for  each  particular  case,  bearing 
in  mind  that  the  greater  the  number  of  steps  for  a given 
length  of  reamer,  the  less  work  will  be  left  for  the  finishing 
reamer. 


31.  If  a number  of  taper  reamers  of  the  same  size  and 
taper  are  required,  and  especially  if  they  are  constantly  in 
use  and  must  frequently  be  reground  or  replaced,  a gauge 
to  which  they  can  be  fitted  becomes  an  absolute  necessity. 
The  gauge  may  be  a hole  of  proper  size  and  taper  in  a cylin- 
drical piece  of  tool  steel  that  has  been  hardened  and  ground. 
With  careful  use,  such  a gauge  will  last  practically  a lifetime. 


26 


TOOLMAKING. 


25 


ENLARGING  WORN  SOLID  REAMERS. 

32.  In  spite  of  the  most  careful  use,  reamers  will  wear, 
and  hence  will  ream  holes  smaller  than  the  standard  size 
for  which  they  were  made.  The  question  of  when  a reamer 
has  worn  enough  to  become  unserviceable  must  be  decided 
on  its  own  merits  in  each  particular  case  ; it  is  utterly  impos- 
sible to  lay  down  any  rule  for  it.  When  a finishing  reamer 
has  worn  down  too  much,  it  may  either  be  converted  into  a 
roughing  reamer,  or  be  restored  to  its  former  size  by,  anneal- 
ing it  and  then  upsetting  it  sufficiently  with  a round-nosed 
calking  tool  to  allow  it  to  be  reground  to  its  former  size 
after  hardening.  To  upset  it,  the  reamer  may  be  held 
between  lead  jaws  in  a vise;  the  calking  tool  is  then  applied 
to  the  face  of  the  cutting  edges,  a little  below  the  edge. 
When  driven  into  the  face  with  a hammer,  it  forces  the 
edge  outwards,  thus  making  the  reamer  larger  in  diameter. 
This  operation  of  enlarging  a worn  reamer  can  rarely  be 
done  more  than  once. 


SHELL  REAMERS. 

33.  Shell  reamers  may  be  given  the  same  number  of 
teeth,  and  have  their  cutting  edges  formed  in  the  same  man- 
ner, as  any  solid  reamer.  In  making  a shell  reamer,  it  is 
well  to  make  the  hole  slightly  smaller  and  then  grind  it  to 
correct  size  after  hardening  and  tempering.  The  hardening 
process  is  likely  to  change  the  diameter  of  the  hole,  and  is 
sure  to  throw  it  out  of  round ; hence,  in  order  that  the  reamer 
may  fit  its  arbor  well,  the  hole  must  be  ground.  The  cutting 
edges  may  then  be  ground  while  the  reamer  is  mounted  on 
its  arbor.  If  the  reamer  is  worn  below  size,  it  may  often  be 
restored  by  the  means  described  in  Art.  32 ; however,  since 
it  is  not  possible  to  tell  whether  the  hole  will  enlarge  or 
become  smaller,  there  is  no  certainty  about  whether  it  can 
be  used  on  the  same  arbor  afterwards.  If  the  hole  is  made 
tapering,  it  can  usually  be  done;  if  the  hole  is  straight,  this 
is  rather  uncertain. 


26 


TOOLMAKING. 


§26 


ROSE  REAMERS. 

34.  As  rose  reamers  cut  on  the  end  only,  the  grooves 
with  which  they  are  to  be  provided  along  their  cylindrical 
surface  need  not  be  of  the  same  shape  as  those  of  other 
reamers.  A semicircular  milling  cutter  having  a width 
equal  to  about  one-quarter  the  diameter  of  the  rose  reamer 
will  cut  an  excellent  groove,  the  depth  of  which  may  be 
about  two-thirds  the  width  of  the  cutter.  After  hardening 
and  tempering,  grind  and  leave  the  cylindrical  part  truly 
circular.  True  up  the  extreme  cutting  edges  at  the  same 
time  and  bring  to  a sharp  cutting  edge  again  by  careful 
grinding  on  a beveled  grinding  wheel,  or  by  oilstoning. 

35.  Rose  reamers  for  small  work  can  be  made  advan- 
tageously of  drill  rod,  which  can  be  obtained  very  closely 
agreeing  with  the  diameter  corresponding  to  its  nominal 
size.  Commercial  drill  rod  in  sizes  up  to  No.  1,  Brown  & 
Sharpe  drill  gauge,will  rarely  vary  more  than  TqVo'  inch  from 
its  true  size  and  be  surprisingly  straight.  Such  small  rose 
reamers  are  often  made  without  flutes,  and  answer  quite 
well  where  extreme  accuracy  is  not  required.  Furthermore, 
they  are  quite  cheaply  made  in  a speed  lathe  and,  since  they 
are  hardened  only  at  the  very  cutting  end,  need  no  grinding 
for  ordinary  work.  When  making  small  reamers  from  drill 
rod,  it  is  advisable  to  neck  them  down  back  of  the  cutting 
edge,  as  shown  in  Fig.  14;  the  diameter  at  the  neck  may  be 
from  yoVo  t°  tf6t  inch  smaller  than  the  rod.  It  has  been 


Fig.  14. 

observed  when  hardening  drill  rod  at  the  end,  that  it  will 
often  swell,  that  is,  become  slightly  larger  in  diameter, 
directly  back  of  the  hardening.  By  necking  down  the  rose 
reamer 'where  the  swelling  is  likely  to  occur,  any  danger  of 
having  the  reamer  bind  in  the  hole  is  obviated. 


§26 


TOOLMAKING. 


27 


Rose  reamers  made  of  drill  rod  up  to  and  including  No.  1 
gauge  size  may  be  given  three  cutting  edges.  After  bevel- 
ing the  end  of  the  reamer  in  the  lathe,  the  flutes  may  be  filed 
in  with  a three-square  file,  preferably  filing  them  as  shown  in 
the  illustration,  which  has  purposely  been  enlarged  in  order 
to  show  the  cutting  edges  clearly.  If  thus  made,  the  reamer, 
while  cutting,  will  tend  to  push  the  chips  ahead ; this  feature 
contributes  to  the  smoothness  of  the  hole  reamed  by  it,  since 
there  is  little  danger  then  of  the  flutes  becoming  clogged. 
After  giving  clearance  to  the  cutting  edges,  harden  at  the 
very  end  and  temper.  A very  smooth  hole  can  be  obtained 
if  the  outer  corner  of  each  cutting  edge  is  slightly  rounded 
over  with  an  oilstone. 


CHUCKING  REAMERS  FOR  ROUGHING. 

36.  While  rose  reamers  are  commonly  used  in  screw 
machines,  chucking  machines,  and^  lathes  for  roughing  out 
cored  holes,  they  are  really  better  adapted  to  finish  reaming. 
Other  forms  of  reamers  are  better  adapted  to  roughing  out, 
as  they  will  cut  much  faster  and  be  more  economical  in 
maintenance.  One  of  the  best 
reamers  for  roughing  out  cored 
holes  in  chucking  work  is  a 
reamer  that  may  be  called  a 
multiple-lipped  twist  drill, 
made  with  three  or  four  cutting 
edges.  They  are  usually  made 
as  shell  reamers  in  the  larger 
sizes,  and  as  solid  reamers  in  the 
smaller  sizes.  The  flutes  are  cut 
on  a right-handed  helix  of  such 
pitch  as  to  give  the  cutting  edges 
an  angle  of  about  15°  with  a plane  passing  through  the  axis. 
An  end  view  of  a four-lipped  twist  drill  is  shown  in  Fig.  15. 

Milling  cutters  suitable  for  making  this  form  of  groove 
can  be  obtained  of  the  Brown  & Sharpe  Manufacturing 
Company,  Providence,  Rhode  Island,  on  regular  order  for 


28 


TOOLMAKING. 


§ 26 

sizes  up  to  3 inches.  These  drills  are  sharpened,  like  twist 
drills,  by  grinding  on  the  ends.  They  are  made  like  rose 
reamers  with  no  relief  given  to  the  lands  between  the 
grooves,  the  lands  serving  to  guide  the  reamer  straight. 
The  helical  grooves  give  keen  cutting  edges  and  insure  that 
the  reamer  clears  itself  of  chips.  If  made  as  a shell  reamer, 
the  hole  must  be  ground  to  size  after  hardening  and  temper- 
ing. The  outside  may  then  be  ground  to  size,  with  a taper 
of  about  .001  inch  to  the  inch,  being  smallest  at  the  back 
end,  to  prevent  roughing  up  or  binding  in  the  hole,  while  the 
reamer  is  mounted  on  its  own  arbor.  As  reamers  of  this 
kind  are  intended  for  roughing  out,  it  is  unnecessary  to 
grind  them  to  correct  size  within  a fractional  part  of  a 
thousandth  of  an  inch.  This  applies  to  other  roughing 
reamers  as  well.  For  a four-lipped  twist  drill,  the  width  of 
the  lands  may  be  about  one-tenth  the  diameter  of  the  drill. 
The  hole,  if  the  reamer  is  made  as  a shell  reamer,  should  in 
general  not  be  larger  than  one-half  the  outside  diameter. 
The  grooves  may  be  spaced  slightly  irregular,  preferably  so 
that  opposite  cutting  edges  are  on  the  same  diameter.  For 
small  work,  three  grooves  will  work  fairly  satisfactorily. 


ADJUSTABLE  REAMERS. 

37.  Reamers  are  made  adjustable  within  narrow 
limits  for  two  different  purposes.  In  the  first  place,  reamers 
are  made  adjustable  for  the  purpose  of  readily  taking  up  the 
wear  and  allowing  several  sharpenings  without  losing  the 
standard  size.  Such  reamers  are  purposely  so  made  that 
the  size  to  which  they  are  set  cannot  be  varied  without 
machine  work,  the  idea  being  to  keep  the  user  from  tamper- 
ing with  the  size.  On  the  other  hand,  reamers  may  be  made 
adjustable  for  the  purpose  of  allowing  the  diameter  of  the 
hole  reamed  by  them  to  be  slightly  varied  either  way  from 
the  standard  size.  They  are  then  made  to  be  adjusted  by 
the  user,  while  the  former  is  adjusted  by  the  toolmaker.  To 
distinguish  between  the  two  designs,  many  toolmakers  con- 
fine the  term  adjustable  reamer  to  reamers  that  cannot  be 


TOOLMAKING. 


29 


§26 

adjusted  without  machine  work,  and  call  a reamer  intended 
for  varying  the  diameter  of  the  hole  an  expanding 
reamer. 

38.  There  is  an  infinite  number  of  designs  possible  for 
making  a reamer  adjustable.  Some  of  these  are  shown; 
these  designs  are  not  offered  as  finality,  but  as  suggestions. 
In  general,  the  smaller  sizes  of  adjustable  and  expanding 
reamers  can  be  bought  of  the  manufacturers  more  cheaply 
than  they  can  be  made,  and  it  is  only  in  the  larger  sizes  or 
in  special  reamers  that  there  is  any  economy  in  making  them 
in  the  tool  room. 

39.  The  design  of  reamer  shown  in  Fig.  16  is  an  adjust- 
able reamer.  It  consists  of  a body  containing  a number  of 
dovetailed  grooves  cut  at  an  inclination  to  the  axis.  Blades 
that  form  the  cutting  edges  are  carefully  fitted  to  these 
slots.  These  blades  butt  against  the  shoulder  of  the  collar  a 
at  the  back  end  and  are  firmly  held  against  it  by  the  lock- 
nut b.  In  order  to  show  the  blades  clearly,  the  locknut  has 


Fig.  16. 

been  omitted  in  the  end  view.  When  the  reamer  has  worn 
sufficiently  below  size  to  make  it  unserviceable,  the  nut  b is 
loosened,  the  blades  are  partially  driven  out,  and  the  shoulder 
of  the  collar  a is  faced  off  sufficiently  to  make  the  reamer 
slightly  over  size  when  the  blades  are  driven  home  again. 
The  blades  are  then  reground  and  stoned  to- standard  size. 

The  design  shown  can  readily  be  converted  into  an  expand- 
ing reamer  by  placing  a nut  in  the  place  occupied  by  the 
collar  a.  By  varying  the  position  of  the  two  locknuts,  the 
blades  can  then  be  expanded  or  contracted  slightly.  In 


30 


TOOLMAKING. 


§26 


designing  such  a reamer,  it  is-well  to  bear  in  mind  that  the 
range  of  expansion  for  a given  longitudinal  movement  can 
be  increased  by  making  the  inclination  of  the  slots  with  the 
axis  greater.  The  slots  are  usually  planed  in  on  the  planer 
or  shaper.  This,  in  general,  is  cheaper  than  milling  them. 

40.  The  design  shown  in  Fig.  16  is  suitable  for  holes 
that  pass  clear  through  the  work.  If  the  hole  is  blind,  how- 
ever, it  cannot  be  reamed  to  the  bottom,  since  the  locknut 
projects  beyond  the  end  of  the  blades.  The  design  shown 
in  Fig.  17  may  then  be  adopted.  In  this,  the  slots  are 


Fig.  17. 


inclined  the  opposite  way  from  that  shown  in  Fig.  16.  Instead 
of  a locknut,  a flat-headed  screw  is  used  at  the  front  end, 
which  bears  against  a shoulder  on  the  under  side  of  the 
blades.  By  means  of  this  screw  and  the  locknut  at  the  back, 
the  blades  may  be  forced  outwards  or  drawn  inwards.  The 
design  illustrated  is  for  an  expanding  reamer;  it  may 
readily  be  used  for  an  adjustable  reamer  by  making  the 
locknut  at  the  back  end  screw  against  a shoulder.  In  that 
case,  to  adjust  it,  the  shoulder  is  turned  down;  the  back 
nut  is  then  screwed  tight  against  it  and  the  front  screw 
hove  up  in  order  to  lock  the  blades. 

43.  An  inserted-blade  expanding  reamer  of  somewhat 
different  construction  is  shown  in  Fig.  18.  In  this  design, 
the  blades  are  flat  and  consequently  easily  fitted.  The 


31 


§ 26  TOOLMAKING. 


Section  on//ne  A B. 
Fig.  18. 


blades  are  beveled  at  the  front  and  back;  the  slots  that 

receive  the  blades  are  also  beveled 
at  the  back  end.  A central  tapered 
pin  bears  against  the  bottom  of  the 
blades;  by  screwing  the  pin  in  or 
out  and  screwing  up  the  locknut,  the 
blades  are  forced  outwards  or  drawn 
inwards.  The  blades,  after  harden- 
ing and  tempering,  require  to  be 
ground  flat  and  parallel  on  the  sides; 
they  must  be  a good  fit  in  the  slots. 
The  inner  face  of  the  blades,  which 
bears  against  the  taper  pin,  should 
also  be  ground  straight  on  a surface 
grinder.  The  taper  pin  may  be 
hardened  and  drawn  to  a purple 
color;  it  should  then  be  ground 
true.  After  assembling  the  reamer, 
adjust  the  pin  and  locknut  so  as  to 
be  midway  between  its  two  extreme 
positions  and  then  grind  the  outside 
to  standard  size.  Relieve  and  taper 
off  the  ends  as  in  any  other  reamer. 
The  locknut  may  preferably  be  hard- 
ened, but  the  body  of  the  reamer 
should  be  left  soft.  The  body  should 
be  made  of  tool  steel  in  the  smaller 
sizes,  i.  e.,  for  sizes  below  1^  inches. 
Above  this  size,  it  may  be  made  of 
machinery  steel.  The  design  shown 
in  Fig.  18  is  suitable  for  reamers 
from  f inch  up. 


42.  The  most  common  forms  of 
expanding  reamers  are  shown  in 
Fig.  19.  In  both  designs,  the  ream- 
er is  made  at  first  exactly  as  if  it 
were  a solid  reamer;  an  axial  hole  is 


32 


TOOLMAKING. 


§26 


then  drilled  and  tapped  for  the  adjusting  screw,  and,  finally, 
the  reamer  is  split.  Referring  to  Fig.  19  (tf),  the  reamer  is 
split  at  the  end.  Screwing  the  taper-headed  screw  inwards 


(b) 

Fig.  19. 


expands  the  reamer;  it  is  then  locked  by  the  locknut  shown. 
This  reamer  becomes  large  at  the  end. 

In  the  design  shown  in  Fig.  19  ($),  the  end  is  left  solid, 
but  the  reamer  is  split  by  sinking  in  a narrow  milling  cutter 
right  back  of  the  end.  The  slots  may  commence  at  a dis- 
tance from  the  end.  equal  to  about  one  and  one-half  times 
the  diameter  of  the  reamer.  The  length  of  the  slots  should 
be  about  four  times  the  diameter  of  the  reamer.  The  num- 
ber of  parts  into  which  the  reamer  is  split  varies  with  the 
diameter.  Reamers  up  to  -J  inch  may  be  split  into  two  parts; 
up  to  § inch,  into  three  parts;  and  above  that  size,  into  four 
parts. 

Split  expanding  reamers  are  the  cheapest  expanding  ream- 
ers to  construct ; they  are  open  to  the  objection,  however, 
that  expanding  does  not  change  their  diameter  uniformly 
throughout  their  length.  Whether  this  objection  is  serious 
enough  to  prohibit  their  employment  for  a particular  case 
must  be  decided  upon  the  merits  of  the  case. 

The  diameter  of  split  expanding  reamers  depends  on  the 
service  expected  of  them.  If  they  are  made  expanding  simply 


§26 


TOOLMAKING. 


33 


in  order  to  be  able  to  ream  holes  to  a standard  size,  they  should 
originally  be  ground  and  stoned  to  the  standard  diameter. 
If  they  are  intended  to  ream  holes  at  will  slightly  above  or 
below  standard  size,  they  must  be  made  slightly  under  the 
Standard  size. 


FORMED  REAMERS. 

43.  When  holes  that  are  neither  straight  nor  conical 
(tapering)  are  to  be  finished  by  reaming,  so-called  formed 
reamers  must  be  used.  Some  shapes  of  formed  reamers 
can  be  readily  ground  in  the  ordinary  grinding  machine; 
others,  again,  require  special  apparatus  for  their  production. 
Formed  reamers  in  general  are  avoided  as  much  as  possible, 
as  they  are  very  expensive  in  first  cost  and  exceedingly  diffi- 
cult to  duplicate  if  a great  degree  of  accuracy  is  required. 
There  are  some  jobs,  however,  that  simply  cannot  be  done 
without  them;  in  that  case,  the  toolmaker  must  use  his 
ingenuity  as  to  the  best  way  of  grinding  them  to  correct 
size  and  shape. 


FOUR-SQUARE  REAMERS. 

44.  If  a long  hole  is  to  be  finished  very  true  and  very 
smooth,  as,  for  instance,  the  bore  of  a rifle  barrel,  a type  of 
reamer  differing  entirely  from  any  shown  heretofore  must 
be  used.  This  type,  which  is  shown  in  Fig.  20,  is  very  little 
known  outside  of  armories,  where  it  is  used  practically  to 
the  exclusion  of  all  other  reamers  for  the  purpose  of  finish- 
reaming the  bore  of  gun  barrels.  It  is  well  adapted  to 
similar  machine-shop  work. 

The  reamer  is  made  of  square  tool  steel.  The  four  sides 
are  hollowed  out,  as  shown  in  the  end  view.  If  the  reamer 
is  large,  this  may  be  done  in  the  milling  machine,  shaper, 
or  planer;  for  small  reamers,  it  may  be  done  by  filing.  The 
reamer  is  then  hardened  and  tempered  and  ground  on  the 
surface  grinder,  grinding  the  corners  only,  until  it  is  per- 
fectly straight  and  parallel.  Its  diameter  across  corners  is 


34 


TOOLMAKING. 


26 


made 


10  0 6 


inch  smaller  than  the  diameter  of  the 
hole  to  be  reamed.  It  is  then  stoned 
carefully  to  give  very  smooth  edges, 
using  the  finest  grade  of  Arkansas  oil- 
stone. The  extreme  ends  are  slightly 
tapered  off  by  stoning.  In  use,  a slip  of 
hard  wood,  as  b , which  extends  the  whole 
length  of  the  reamer,  is  inserted  between 
one  side  of  the  reamer  and  the  walls  of 
the  hole.  This  causes  the  edges  a , a to 
cut.  After  passing  through  the  hole,  a 
strip  of  tissue  paper  is  placed  between 
the  reamer  and  the  slip  of  wood;  this 
causes  the  reamer  to  take  another  cut. 
This  is  repeated  until  the  hole  is  the  cor- 
rect size.  Copious  lubrication  is  essen- 
tial to  good  work.  The  slip  of  hard 
wood  may  be  confined  longitudinally  by 
two  pins,  as  shown.  A reamer  of  this 
kind  is  suited  only  for  removing  minute 
amounts  of  metal.  But,  on  the  other 
hand,  it  will  produce  a degree  of  finish 
that  cannot  be  excelled  by  any  other 
kind  of  reamer.  It  requires  pulling 
through  the  hole  in  order  to  work  best. 
A four-square  reamer  may  be  made  with- 
out hollowing  out  the  sides;  it  is  then, 
however,  more  difficult  to  sharpen  when 
worn.  The  length  of  a four-square  ream- 
er may  be  about  eight  times  its  diam- 
eter. 


fig.  20. 


FRONT  CHAMFER. 

45.  Straight  reamers  intended  to 
cut  at  their  ends  only,  like  rose  reamers 
and  chucking  reamers,  are  to  be  made 
with  a very  slight  taper  for  clearance. 


26 


TOOLMAKING. 


35 


This  taper  is  so  slight  that  the  part  back  of  the  cutting  edges 
still  serves  as  a guide.  Straight  reamers  that  have  their 
cutting  edges  formed  on  their  circumference  require  the 
front  end  to  be  slightly  chamfered  off  in  order  that  they 
may  enter  the  hole  easily. 


COUNTERBORES. 

46.  The  design  of  a counterbore  depends  on  several 
conditions,  which  are:  the  nature  of  the  metal  it  is  to  be 
used  for,  the  range  in  the  size  of  holes  to  be  counterbored, 
the  number  of  holes  to  be  counterbored,  and  the  distribution 
of  metal  around  the  hole. 


SOL-ID  COUNTERBORE. 

47.  When,  a counterbore  is  to  be  used  for  a relatively 
small  number  of  holes  and  is  to  be  thrown  away  after  serving 
its  purpose,  it  is  advisable  to  adopt  a cheap  construction  in 
order  to  reduce  first  cost  to  the  lowest  limit.  Probably  the 
cheapest  counterbore  that  can  be  made  is  the  two-lipped 
flat  counterbore  with  a solid  teat,  which  is  shown  in 
Fig.  21.  This  can  be  forged  very  near  to  shape,  and  needs 


but  little  machine  work  and  filing  to  make  it  serviceable. 
After  forging,  center  at  both  ends;  turn  the  shank  to  the 
required  size;  then  reverse  and  turn  up  the  teat,  finishing 
it  with  a fine  file.  Turn  the  counterbore  to  correct  size  and 


36 


TOOLMAKING. 


§26 


face  the  cutting  edges.  Finish  by  filing  the  sides  smooth 
and  give  clearance  to  the  cutting  edges.  If  the  counterbore 
is  to  be  used  for  wrought  iron  or  steel,  a keen  cutting  edge 
may  be  given  by  filing  as  shown  at  a in  dotted  lines.  For 
cast  iron  and  brass,  it  is  better  to  leave  the  cutting  edges 
without  any  front  rake.  A slight  relief  may  be  given  to  the 
faces  b , b to  prevent  them  from  binding  in  case  the  counter- 
sinking is  to  be  carried  to  an  appreciable  depth.  If  the 
counterbore  is  intended  only  for  squaring  up  the  face 
around  a hole,  no  relief  need  be  given  to  b}  b.  Only  the 
cutting  edges  need  be  hardened;  they  may -be  drawn  to  a 
straw  color.  The  process  of  hardening  leaves  the  teat  hard ; 
some  toolmakers  draw  the  end  of  the  teat  to  a blue  color  by 
inserting  it  into  red-hot  lead  for  the  purpose  of  preventing 
i's  breaking  off.  Since  the  teat  is  most  liable  to  break  off 
close  to  the  cutting  edges,  however,  and  since  it  cannot  be 
drawn  to  a spring  temper  clear  up  to  the  edges  without  par- 
tially softening  them,  many  toolmakers  believe  that  it  is  a 
waste  of  time  to  draw  the  teat  to  a higher  color  than  the 
cutting  edges. 

48.  When  a hole  is  drilled  close  to  a projection,  and 
when  it  is  required  that  the  counterbore  should  cut  part  of 
the  projection  away,  it  is  better  to  use  a counterbore  with 
four  cutting  edges.  This  may  be  turned  down  from  bar 
tool  steel  and  have  its  cutting  edges  formed  by  cutting 
grooves  with  a 60°  cutter  in  the  milling  machine.  The 
grooves  may  be  cut  on  a right-handed  helix,  making  an 
angle  of  about  15°  with  a plane  passing  through  the  axis  of 
the  counterbore  if  it  is  intended  for  wrought  iron  and  steel. 
For  brass  and  cast  iron,  the  grooves  may  be  straight.  The 
cutting  edges  are  to  be  given  clearance  by  filing;  it  is 
advisable  to  give  clearance  to  the  lands  also.  The  counter- 
bore will  then  have  much  less  tendency  to  spring  from  the 
projection  while  cutting  part  of  it  away. 

49.  Solid  counterbores,  while  cheap  in  first  cost,  are 
open  to  two  serious  objections.  In  the  first  place,  they  are 
difficult  to  sharpen;  in  the  second  place,  they  are  limited  in 


26 


TOOLMAKING. 


37 


their  range  to  holes  as  large  as  the  teat  or  larger.  They 
can  be  adapted  to  holes  larger  than  the  teat  by  forcing  a 
bushing  over  it.  As  it  is  rather  difficult  to  remove  the 
bushing,  this  method  of  making  a counterbore  adapted  to 
several  sizes  of  holes  can  only  be  considered  as  a makeshift, 
especially  as  the  difficulty  of  properly  sharpening  it  is 
retained.  Two-lipped  and  four-lipped  solid  counterbores 
are  sharpened  by  grinding — on  the  sides,  in  case  of  a two- 
lipped counterbore,  and  on  the  flat  side  of  the  grooves  in 
case  of  a four-lipped  counterbore. 


BUILT-UP  COUNTERBORES. 

50.  Inserted-Teat  Counterbore. — The  counterbore 
shown  in  section  in  Fig.  22  overcomes  the  objections  raised 
against  the  solid  counterbore.  It  is  slightly  more  expensive 
to  make,  but  will  serve  for  a greater  variation  in  size  of  hole 
than  any  other.  In  addition,  it  can  be  sharpened  very 
easily.  As  shown  in  the  figure,  it  has  a central  hole  bored 
to  receive  the  shank  of  the  teat,  which  is  held  in  place  by 
the  setscrew.  After  turning  the  outside,  the  central  hole 


Fig.  22. 


may  be  bored  true  and  reamed,  running  the  large  end  of 
the  counterbore  in  the  steady  rest.  The  grooves  may  then 
be  cut  between  centers  in  the  milling  machine,  or  the 
counterbore  may  be  held  in  a chuck,  as  is  most  convenient. 
A 60°  milling  cutter  should  be  used  if  four  cutting  edges 
are  given.  For  wrought  iron  and  steel,  the  grooves  may 
be  cut  along  a right-handed  helix;  for  brass  and  cast  iron, 
they  may  be  straight.  After  hardening  and  tempering,  the 
hole  should  be  lapped  out;  teats  of  the  desired  sizes  may- 
then  be  turned  and  fitted  to  the  counterbore.  These  teats 


38 


TOOLMAKING. 


§ M 

may  be  hardened  at  the  end  and  drawn  to  a straw  color. 
Unless  the  counterbore  is  used  for  exceptionally  fine  work, 
there  is  little  need  of  grinding  the  teats  to  run  true.  As 
they  are  to  be  hardened  at  the  extreme  end  only,  there  is 
little  likelihood  of  their  springing  sufficiently  to  interfere 
with  the  working.  The  shank  of  the  teat  should  be  a good 
sliding  fit,  so  that  it  may  be  easily  removed  when  the  set- 
screw is  loosened.  The  counterbore  can  readily  be  sharp- 
ened by  grinding  on  the  end  after  the  teat  is  removed. 

51.  Inserted-Cutter  Counterbores. — When  but  very 
few  holes  of  a special  size  are  to  be  counterbored,  and  there 
is  little  likelihood  of  the  counterbore  ever  being  wanted 
again,  the  simple  form  shown  in  Fig.  23  may  be  adopted. 
Its  chief  recommendation  is  its  cheapness.  The  objection- 
able feature  is  that  it  can  take  but  a relatively  light  cut, 
which  requires  careful  feeding  to  prevent  breakage  of  the 
cutter.  It  consists  of  a bar  that  fits  the  hole  to  be  counter- 
bored,  and  a cutter  driven  into  a circular  hole  drilled  clear 
through  the  bar.  For  small  counterbores,  the  cutter  may 
be  made  of  drill  rod.  Referring  to  Fig.  23,  after  the  bar  is 
turned  to  a fit,  the  hole  for  the  cutter  is  drilled  and  reamed 


Fig.  23. 


and  a blank  piece  of  drill  rod  of  sufficient  length  driven  in. 
This  is  then  turned  to  the  correct  diameter  and  faced  on 
the  front  side.  It  is  next  driven  out  of  the  bar  and  filed  to 
a cutting  edge,  as  shown,  giving  front  rake  for  wrought  iron 
or  steel.  The  cutter  is  now  hardened  all  over  and  driven 
home  again. 

52.  For  large  work,  a counterbore  may  be  made  as 
shown  in  Fig.  24.  The  bar  is  slotted  and  a flat  cutter  is 
closely  fitted  to  it;  the  cutter  is  confined  by  a key,  as 
shown.  A moderate  range  of  variation  in  the  diameter  of 


§2G 


TOOLMAKING. 


39 


the  counterbored  hole  is  obtained  by  setting  the  cutter  out 
of  center.  The  cutter  is  readily  sharpened.  Whether  to 
harden  the  end  of  the  bar  or  not  must  be  decided  upon 
the  merits  of  the  case.  Many  toolmakers  believe  that  it  is 


the  best  plan  to  leave  the  end  of  the  bar  soft  and  to  turn  it 
down  sufficiently  to  receive  a hardened  bushing  that  is  a 
good  snug  fit  and  kept  from  turning  by  a pin. 


HOLLOW  MILLS. 


SOLID  HOLLOW  MILLS. 


53.  Hollow  mills  are  chiefly  used  for  screw-machine 
and  turret-lathe  work  for  roughing  down  and  finishing  stock 


fig.  25. 


preparatory  to  threading.  When  intended  for  finishing, 
they  are  usually  made  adjustable.  For  roughing  out,  solid 
mills  are  preferred,  since,  in  general,  they  are  not  as 


C.  5.  IIJ.— 33 


40 


TOOL  MAKING. 


26 


springy  as  adjustable  mills.  Hollow  mills  may  be  made 
in  a great  variety  of  forms.  For  small  work,  the  most 
common  form  is  the  solid  mill  shown  in  Fig.  25.  This  is 
commonly  made  with  four  cutting  edges  formed  by  milling 
with  a side  milling  cutter  of  about  double  the  outside 
diameter  of  the  mill.  In  order  that  the  mill  may  work 
easily,  it  must  be  relieved  inside  by  filing  it  as  shown.  The 
rear  of  the  mill  is  to  be  bored  larger  in  diameter  than  the 
cutting  end.  This  allows  it  to  clear  on  long  cuts,  and,  at 
the  same  time,  makes  it  easier  to  file  the  clearance.  In 
making  the  mill,  it  is  advisable  to  mill  out  the  cutting  edges 
before  giving  the  clearance  inside;  if  this  is  done,  the  clear- 
ance can  be  filed  more  rapidly,  since  there  is  then  but  a 
relatively  small  quantity  of  metal  to  be  removed.  The 
milling  cutter  is  to  be  set  by  trial  until  it  makes  a about 
one-sixth  the  inside  diameter  and  b about  eight-tenths  of 
the  inside  diameter.  The  back  of  the  mill  may  be  bored 
about  one  and  one-fifth  times  the  diameter  at  the  front 
end.  The  faces  on  which  the  cutting  edges  are  located  are 
usually  spaced  equidistant  and  lie  in  planes  passing  through 
the  axis.  The  mill  is  hardened  as  far  back  as  the  end  of 
the  milling  and  drawn  to  a straw  color  from  the  back,  set- 
ting it  on  a red-hot  piece  of  iron.  All  sharpening  is  done 
by  grinding  on  the  end. 

54.  An  adjustable  hollow  mill  may  be  constructed  in  the 
same  manner  as  the  adjustable  spring  die  shown  in  Fig.  3, 
using  a clamp  collar  to  adjust  it. 


INSERTED-BLADE  HOLLOW  MILLS. 

55.  For  large  work,  hollow  mills  may  be  made  with  in- 
serted blades,  constructing  them  if  desired  non-adjustable 
in  the  same  manner  as  the  solid  die  shown  in  Fig.  2.  If 
desired  adjustable,  a design  similar  to  that  shown  in  Fig.  4 
may  be  adopted. 

56.  A very  good  .design  of  a hollow  mill  with  removable 
blades  and  adjustable  for  sizes  within  narrow  limits,  is  shown 


§26 


TOOLMAKING. 


41 


in  Figs.  26  and  27.  Fig.  26  shows  the  mill  taken  apart; 
Fig.  27  shows  it  assembled. 

The  mill  consists  essentially  of  a body  a in  which  a number 
of  slots,  as  b , are  cut  at  an  inclination  to  the  axis.  These 
slots  receive  the  cutters  c , c , which  are  a loose  fit  in  them. 


Fig.  26. 

The  cutters  are  rectangular  in  cross-section;  their  rear  end 
butts  against  the  adjusting  nut  d.  They  are  held  in  place 
by  a tapering  collar  e,  which  surrounds  them  and  is  pushed 
home  by  a locknut  located  at  the  front  end.  The  inside 
of  the  collar  e is  bored  out  sufficiently  large  to  clear  the 
body  a and  to  fit  the  outside  of  the  cutters,  which  extend 
slightly  above  the  tapered  surface  of  a.  Clearance  spaces 


Fig.  27. 

for  the  reception  of  the  chips  are  cut  between  the  slots,  as 
shown  at  ft  f.  These  clearance  spaces  communicate  with  the 
outside  by  an  opening  cut  through  the  body  and  a corre- 
sponding opening  in  the  collar.  To  set-the  mill  to  a smaller 
size,  the  locknut  g is  loosened  in  order  to  loosen  the  cutters. 


42 


TOOLMAKING. 


§26 


These  are  then  pushed  forwards,  and,  consequently,  closed 
in  by  turning  the  adjusting  nut  d forwards.  Tightening 
the  locknut  forces  the  taper  collar  over  the  cutters  and  thus 
locks  them.  In  order  to  set  the  mill  to  a larger  diameter, 
the  cutters  are  loosened  by  unscrewing  the  locknut;  the 
nut  d is  then  turned  back  and  the  cutters  pushed  against  it 
by  hand.  They  are  locked  again  by  screwing  the  locknut 
home. 

A hollow  mill  constructed  in  accordance  with  this  design 
is  rather  expensive  as  far  as  first  cost  is  concerned.  It  is 
very  economical  in  its  maintenance,  however,  since  new 
cutters  can  be  made  for  it  at  a very  slight  cost.  By  making 
the  cutters  of  suitable  shape,  the  mill  can  be  adapted  to  a 
limited  range  of  sizes. 

57.  When  making  the  mill,  it  is  advisable  to  cut  the 
bottom  of  the  slots  at  the  same  distance  from  the  axis,  in 


order  that  the  cutters  may  all  be  alike.  After  the  first  set 
of  cutters  has  been  made,  a filing  jig  may  be  constructed, 
in  which  spare  cutters  can  be  filed  exactly  alike  in  height, 
length,  and  shape  of  cutting  edge.  A simple  filing  jig  for 
this  purpose  is  shown  in  Fig.  28.  It  consists  of  two  parts 
doweled  together.  One  of  the  cutters  out  of  the  first  set 
made  serves  as  a model;  it  is  placed  between  the  two  parts 
of  the  jig,  butting  its  rear  end  against  the  stop  a . The  jig 
is  then  worked  down  to  the  height  of  the  cutter  and  is 


§26 


TOOLMAKING. 


43 


beveled  to  suit  it;  as  the  cutter  is  hardened,  this  can  be 
done  readily.  The  jig  is  now  hardened  and  used  to  duplicate 
the  cutters.  It  is  made  in  two  parts  doweled  together  in 
order  to  cheapen  its  construction;  the  act  of  clamping  it  in 
the  vise  clamps  the  soft  cutter  placed  in  it  at  the  same  time, 
thus  obviating  the  necessity  of  any  clamping  device.  The 
filing  jig  must  be  made  of  tool  steel.  Before  the  jig  can  be 
used,  the  cutters  must  be  cut  down  to  the  correct  width  for 
the  slots  in  the  mill  body,  which  should  be  exactly  alike  to 
allow  the  cutters  to  interchange. 


HOLLOW  MILL  FOR  ANNULAR  MILLING. 

58.  Hollow  mills  can  be  used  with  advantage  on  some 
classes  of  work  for  milling  the  outside  of  a cylindrical  pro- 
jection central  with  a hole  passing  through  it,  provided  great 
accuracy  is  not  required.  The  mill  is  then  made  with  a 
central  guide  pin,  as  shown  in  Fig.  29.  This  pin  is  to  be 


Fig.  29. 

hardened  at  the  end  and  drawn  to  a spring  temper.  It  is 
recommended  to  hold  the  pin  by  means  of  a setscrew  to 
allow  ready  removal  when  the  mill  is  to  be  ground.  In 
order  to  facilitate  the  filing  of  the  inside  clearance,  it  is 
advisable  to  bore  out  the  rear  end  of  the  mill  somewhat 
larger  than  its  inside  diameter. 


TOOLMAKING. 

(PART  3.) 


CUTTING  TOOLS  AND  APPLIANCES. 


MILLING  CUTTERS. 


SOLID  MILLING  CUTTERS. 

1.  Number  of  Cutting  Edges  for  Solid  Cutters. — 
iMilling  cutters  up  to  6 inches  in  diameter  are  usually 

TABLE  OF  CUTTING  EDGES  FOR  MILLING  CUTTERS. 


Diameter  of  Cutter. 

Cutting  Edges. 

i 

6 

i 

8 

l 

12 

n 

14 

H 

16 

2 

18 

H 

21 

3 

24 

31 

26 

4 

28 

5 

30 

6 

32 

§27 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


TOOLMAKING. 


§27 


made  solid,  and  above  that  size  they  are  made  with  inserted 
teeth.  The  number  of  cutting  edges  for  solid  milling  cut- 
ters intended  for  general  work  may  be  as  given  in  the  pre- 
ceding table,  which  is  believed  to  conform  very  closely  to 
average  practice. 

The  cutting  edges  are  generally  made  with  a radial  face, 
as  indicated  by  the  dotted  lines  in  Fig.  1 ; the  spaces  on  the 
circumference  may  be  cut  with  a cutter  that  will  produce 
an  angle  of  about  50°  between  the  face  and  the  back  of  the 


tooth.  This  angle  gives  an  ample  depth  to  the  clearance 
spaces,  and,  at  the  same  time,  gives  well-supported  cutting 
edges.  The  milling  cutter  used  for  forming  the  teeth  is  run 
in  deep  enough  to  leave  the  lands  from  .02  to  .04  inch  in 
width,  according  to  the  size  of  the  cutter  that  is  being  made. 
If  teeth  are  cut  on  the  sides  of  the  cutter,  as  shown  in 
Fig.  1,  the  spaces  may  be  cut  with  a milling  cutter  that  will 
produce  an  angle  from  60°  to  70°  between  the  face  and  the 
back  of  the  tooth.  When  milling  the  teeth  on  the  sides, 


§27 


TOOLMAKING. 


3 


the  index  head  cannot  be  left  at  the  90°  mark  or  at  the 
0°  mark,  but  must  be  inclined  a little,  in  order  that  the  cut- 
ter may  make  the  lands  of  equal  width.  The  amount  that 
the  index  head  is  to  be  inclined  depends  on  such  variable 
conditions  that  computation  of  it  is  a difficult  problem;  in 
practice,  it  is  most  rapidly  found  by  an  actual  trial.  After 
cutting  the  teeth,  remove  all  burrs  by  filing,  and  harden. 
The  tempering  is  done  to  advantage  by  inserting  a red-hot 
piece  of  iron  in  the  hole,  thus  making  the  cutter  softest  at 
the  inside.  Draw  to  a good  straw  color.  Since  the  diame- 
ter of  the  hole  is  very  likely  to  change  in  hardening,  it  is 
considered  good  practice  to  make  it  slightly  smaller,  say 
.004  inch  per  inch  diameter  of  the  hole,  and  finish  by  grind- 
ing. To  reduce  the  time  required  for  grinding  the  hole,  it 
may  be  recessed,  as  shown  in  the  sectional  view  of  Fig.  1. 
It  is  recommended  that  the  sides  of  the  boss  be  also  ground 
straight  and  true  with  the  hole. 

2.  Grinding  Milling  Cutters. — The  teeth  are  sharp- 
ened on  a cutter  grinder,  using  the  finger  of  the  grinder  as 
a means  for  obtaining  the  proper  cutting  clearance.  The 
teeth  maybe  given  a clearance  of  about  3°;  that  is,  the 
angle  between  the  face  of  the  teeth  and  the  top  of  the  teeth 
may  be  about  87°.  If  this  degree  of  clearance  is  given,  the 
teeth  will  cut  freely  and  the  cutter  will  last  well.  If  more 
clearance  is  given,  the  cutting  edges  will  dull  quite  rapidly. 
For  grinding  the  teeth  on  the  side  of  a milling  cutter,  a 
small  emery  wheel  must  be  used  in  order  to  get  proper  cut- 
ting clearance  without  touching  the  adjoining  cutting  edge. 
The  method  of  grinding  milling  cutters  does  not  differ  essen- 
tially from  that  employed  in  grinding  reamers;  the  only 
difference  is  that  the  cutting  edges,  as  a general  rule,  are 
finished  entirely  by  grinding,  no  oilstoning  whatsoever  being 
done  on  them. 

In  order  to  get  the  best  work  out  of  a milling  cutter,  it  is 
essential  that  a cutter  grinder  be  used  for  sharpening  it.  It 
is  impossible  to  grind  a cutter  by  hand  so  that  it  will  be 
round.  Milling  cutters  that  cut  only  on  their  ends  when 


4 


TOOLMAKING. 


§27 


used  for  grooving  may  advantageously  be  ground  so  as  to 
be  slightly  smaller  at  the  rear,  say  about  .01  inch  per  inch 
of  length.  When  grinding  cutters,  it  is  well  to  bear  in  mind 
that  only  very  fine  cuts  must  be  taken,  since,  otherwise,  the 
temper  will  be  drawn  from  the  extreme  cutting  edges,  which 
spoils  the  cutter.  The  grinding  of  a cutter  is  a job  that 
cannot  be  hurried  without  inviting  disaster  to  the  cutting 
edges. 

3.  Helical  Cutting  Edges. — When  making  a helical 
milling  cutter,  more  commonly  known  as  a spiral  mill- 
ing cutter,  choose  a helix  that  will  give  the  cutting  edges 
an  angle  of  about  20°  with  a plane  passing  through  the  axis 
of  the  cutter.  It  does  not  make  any  particular  difference 
whether  the  helix  is  right-handed  or  left-handed  when  the 
cutter  is  intended  for  a machine  in  which  the  cutter  arbor  is 
supported  at  the  end.  However,  when  used  for  a machine 
in  which  the  end  of  the  arbor  is  free,  the  helix  should  be 
such  that  the  end  thrust  due  to  the  action  of  the  spiral  cut- 
ting edges  will  tend  to  force  the  arbor  home;  that  is,  if  the 
cutter  is  right-handed,  the  helix  should  be  left-handed;  if 
the  cutter  is  left-handed,  the  helix  should  be  right-handed. 
In  order  that  there  may  be  no  misunderstanding  about  the 
terms  “right-handed”  and  “left-handed”  when  applied  to 
milling  cutters,  they  are  here  defined  as  follows:  Standing 
in  front  of  a milling  machine  with  a horizontal  spindle,  and 
looking  toward  the  spindle,  if  the  milling  cutter  revolves  in 
the  direction  of  the  hands  of  a watch,  it  is  a left-handed  cut- 
ter; if  it  revolves  in  a direction  opposite  to  that  of  the  hands 
of  a watch,  it  is  a right-handed  cutter.  A right-handed 
helix,  however,  is  one  that,  in  advancing,  turns  in  the  direc- 
tion of  the  hands  of  a watch.  A left-handed  helix  turns  in 
a direction  opposite  to  that  of  the  hands  of  a watch. 

4.  Nicked  Teetli. — For  heavy  milling,  spiral  milling 
cutters  with  nicked  teetli  are  an  advantage,  since  they 
break  up  the  chips,  which  enables  a heavier  cut  to  be  taken 
than  is  possible  with  an  ordinary  cutter.  A satisfactory 
way  of  nicking  them  is  as  follows:  Gear  an  engine  lathe  to 


21 


TOOLMAKING. 


5 


cut  a thread  having  a pitch  about  equal  to  the  distance 
between  two  teeth  of  the  cutter,  and  with  a round-nosed 
tool  cut  a half-round  thread  having  a width  equal  to  about 
one-fourth  the  pitch  of  the  thread.  This  is  preferably  done 
before  the  clearance  spaces  are  milled  in  the  cutter.  In- 
serted-teeth  cutters  with  either  straight  or  helical  cutting 
edges,  and  solid  wide  cutters  with  straight  cutting  edges 
may  advantageously  be  nicked  by  cutting  a helical  groove. 


MILLING  CUTTERS  WITH  INSERTED  TEETH. 

5.  Designs. — When  milling  cutters  exceed  0 inches  in 
diameter,  the  cost  of  making  them  of  one  piece  of  tool  steel 


Fig.  2. 


becomes  rather  high;  in  general,  it  is  cheaper  to  make  them 
with  small  teeth  that  are  inserted  in  a body  of  cheap  ma- 
terial, as  cast  iron  or  machinery  steel.  There  is  a great 
variety  of  designs  that  will  make  a satisfactory  cutter.  The 


6 


TOOLMAKING. 


§27 


simplest  design  is  that  in  which  the  cutters  are  fitted  to  dove- 
tail slots  and  driven  home  after  hardening.  In  order  to 
make  a good  job,  the  cutters  must  be  very  carefully  fitted, 
which  makes  renewal  rather  expensive.  Again,  as  the  slots 
must  necessarily  be  dovetailed,  they  are  expensive  ones  to 
make.  These  considerations  have  led  to  designs  that  do  not 
require  such  close  and  expensive  work,  although  they  are 
not  quite  as  simple.  Two  standard  designs  are  shown  in 
Fig.  2.  In  both,  the  cutters  are  rectangular  in  cross-section. 
Owing  to  this  shape,  the  slots  can  be  milled  very  cheaply, 
and  cutters  to  fit  them  can  be  made  at  an  expense  slight  in 
comparison  to  that  involved  in  making  dovetailed  cutters. 
The  design  shown  at  (a)  is  one  that  has  been  adopted  by 
the  Morse  Twist  Drill  and  Machine  Company,  New  Bed- 
ford, Massachusetts.  Rectangular  slots  receive  the  cut- 
ters a , a\  the  body  is  milled  out  between  every  second  pair 
of  slots  to  receive  the  wedge-shaped  piece  of  steel  b,  which 
is  drawn  home  by  means  of  the  fillister-headed  screw  shown, 
and  thus  locks  the  cutters.  A space  is  left  between  the  bot- 
tom of  the  piece  b and  the  body;  this  space  allows  a slight 
variation  in  the  thickness  of  the  cutters. 

In  the  design  shown  at  ( b ),  the  metal  between  every  sec- 
ond pair  of  slots  is  slotted  with  a narrow  slot,  as  c , c.  Before 
cutting  the  narrow  slots,  a hole  is  drilled  clear  through  and 
reamed  “ taper  ” to  receive  the  taper  pins  <?,  which  are 
driven  in  after  the  cutters  are  in  place  and  serve  to  lock 
the  latter.  Driving  the  taper  pins  out  loosens  the  cutters 
sufficiently  to  allow  them  to  be  easily  withdrawn.  This 
design  of  cutter  is  furnished  by  the  Pratt  & Whitney  Man- 
ufacturing Company,  Hartford,  Connecticut. 

6.  Helical  Cutting  Edges.  — Inserted-tooth  milling 
cutters  may  be  given  helical  cutting  edges  for  the  same  pur- 
pose that  solid  cutters  are'  provided  with  them.  Obviously, 
if  a helical  slot  is  cut  into  the  body,  the  cutter  tooth  will  also 
have  to  be  helical  in  order  to  fit  it.  This  is  a very  expensive 
shape  to  produce,  however,  and  can  scarcely  be  made  with 
the  ordinary  machinery  to  be  found  in  a tool  room.  For 


§27 


TOOLMAKING. 


7 


this  reason,  straight  slots  are  cut  at  an  angle  to  a plane  pass- 
ing through  the  axis,  and  straight  cutters  are  universally 
used.  Straight  cutters  set  at  an  angle  are  open  to  one  seri- 
ous objection,  however,  which  is  that  the  front  face  of  the 
cutter  is  not  radial  throughout  its  length,  but  changes  from 
a front  rake  at  one  end  to  a radial  face  in  the  middle  and 
then  to  a negative  rake  at  the  other  end.  This  is  shown  in 
Fig.  3,  which  shows  one  straight  cutter  inserted  at  an  angle. 
In  order  to  bring  out  the  objectionable  point  more  clearly, 
the  diameter  of  the  body  has  been  made  rather  small.  At 
the  end  a , the  face  of  the  cutting  edge  has  front  rake,  as 
indicated  by  the  radial  line  o c.  At  d,  as  indicated  by  the 


radial  lin  tod,  the  cutting  edge  is  radial,  changing  to  a nega- 
tive rake  toward  f.  The  amount  of  negative  rake  at  f is 
shown  by  the  radial  line  o e. 

The  best  way  of  curing  this  defect  is  to  mill  the  cutting 
face  helical  with  a suitable  cutter  set  to  produce  a radial 
face.  To  allow  this  to  be  done,  the  cutter  must  either  be 
made  thicker  throughout,  or  thickened  on  the  cutting  face 
from  beyond  the  body. 

7.  Before  cutting  the  slots,  select  a helix  that  will  give 
the  cutting  edges  an  angle  of  about  20°  with  a plane  passing 
through  the  axis.  Gear  the  milling  machine  to  cut  this 
helix  and  put  the  turned  blank  body  in  the  machine.  With 
a scriber  clamped  to  the  milling-machine  arbor,  scribe  a 
helical  line  on  the  surface  of  the  body.  This  line  will  then 


8 


TOOLMAKING. 


§27 


serve  as  a guide  for  setting  the  index  head  by  trial  to  the 
angle  that  will  give  a straight  slot  coinciding  closely  with 
the  helix.  Unless  the  milling  machine  is  so  arranged  that 
the  index  head  swivels  on  the  platen,  the  slots  will  have  to 
be  cut  with  an  end  mill.  Many  designs  of  milling  machines 
have  a so-called  raising  block  to  which  the  index  head  may 
be  clamped  and  then  swiveled  across  the  platen.  If  this  is 
the  case,  the  slots  can  be  cut  with  a regular  axial  cutter. 
After  the  cutters  have  been  inserted  into  the  slots  and 
locked,  the  milling  machine  is  geared  again  for  the  proper 
helix  and  the  cutting  face  of  each  cutter  milled  helical  and 
radial. 

8.  Proportions  and  Number  of  Teeth. — The  num- 
ber of  cutting  edges  for  milling  cutters  with  inserted  blades 
may  be  about  as  given  in  the  following  table,  which  is  given 
primarily  for  the  purpose  of  aiding  the  toolmaker  in  select- 
ing a suitable  number  of  cutting  edges.  As  opinions  differ 
considerably  in  regard  to  this  matter,  it  must  not  be  ex- 
pected that  all  cutters  will  conform  to  the  table,  which  is 
believed  to  represent  average  practice. 


TABLE  OF  CUTTING  EDGES  FOR  MILLS  WITH 
INSERTED  CUTTERS. 


Diameter. 

Number. 

Diameter. 

Number. 

6 

12 

18 

35 

7 

14 

20 

38 

8 

16 

22 

41 

9 

18 

24 

44 

10 

20 

26 

46 

12 

24 

28 

48 

14 

28 

30 

50 

16 

32 

32 

52 

The  proportions  of  the  cutters  may  be  about  as  follows: 
Referring  to  Fig.  2,  the  thickness  d of  the  cutter  may  be 
about  one-fourth  the  distance  from  one  cutting  edge  to  the 


§27 


TOOLMAKING. 


9 


next  one;  the  depths  may  be  about  three-fourths  the  pitch 
of  the  cutting  edges;  and  the  depth  f of  the  slots  may  be 
about  fifty-five  one-hundredths  of  the  pitch.  By  pitch  is 
here  meant  the  distance  from  one  cutting  edge  to  the  other 
measured  along  the  arc  of  the  circle  circumscribed  about 
the  cutter.  In  other  words,  the  pitch  of  the  cutting  edges 
is  equal  to  the  circumference  of  the  cutter  divided  by  the 
number  of  teeth.  The  cutters  may  be  backed  off  with  a 
milling  cutter  that  will  give  an  angle  of  60°  between  the  front 
and  the  top  of  the  cutter,  as  shown  in  the  figure.  The  back- 
ing off  may  be  carried  forwards  enough  to  leave  a land  of 
about  .03  inch;  after  hardening  and  tempering,  the  cutting 
edges  are  finally  given  by  grinding  the  assembled  mill  in  a 
cutter  grinding  machine,  giving  a relief  of  about  3°. 


FLY  CUTTERS. 

9.  For  work  that  cannot  be  classified  as  repetition  work, 
a fly  cutter  is  often  of  great  advantage  in  milling  odd 
shapes.  Having  but  a single  cutting  edge,  it  is  quite 
cheaply  formed,  even  if  the  shape  to  be  milled  is  quite  com- 
plex. If  properly  made,  it  can  be  sharpened  quite  a number 
of  times  without  materially  changing  its  shape.  Fly  cutters 
are  frequently  made  by  filing  them  to  the  proper  shape; 
when  thus  made,  it  is  very  difficult  to  form  them  so  that 
their  shape  will  not  be  materially  changed  by  successive 
sharpenings.  If  the  method  given  below  is  adopted,  a sat- 
isfactory fly  cutter  will  be  produced;  a further  advantage 
of  this  method  is  that  the  cutter  can  always  be  duplicated 
at  small  expense. 

A fly  cutter  must  not  be  expected  to  cut  as  fast  or  wear 
as  long  as  a regular  milling  cutter;  it  will  reproduce  its 
shape  with  great  exactness,  however.  It  will  be  found  of 
great  advantage  in  making  and  duplicating  forming  tools  of 
irregular  contour  for  the  forming  lathe  and  turret  lathe. 

10.  The  fi  rst  step  is  to  make  a forming  tool,  as  a in 
Fig.  4,  cutting  into  its  front  end  the  shape  that  the  cutter 


10 


TOOLMAKING. 


§27 


is  to  produce.  This  may  be  done  in  whatever  way  is  con- 
venient; it  is  usually  done  by  filing.  This  tool  is  held  in  the 
vise  of  the  milling  machine  and  is  set  at  such  a height  that  its 

top  face  is  level  with  the 
center  of  the  spindle.  The 
soft  cutter,  which,  pre- 
viously, may  have  been 
roughly  filed  to  shape,  is 
then  inserted  in  the  fly- 
cutter  holder  and  locked. 
The  machine  is  now 
started  and  the  forming 
tool  carefully  fed  against 
the  revolving  cutter, 
which  is  thus  cut  to  the 
shape  of  the  forming  tool. 
The  cutter  should  be  fast- 
ened to  the  holder  as  far 
inwards  as  possible  ; it 
should  not  project  farther 
from  it  than  sufficient  to 
just  allow  the  forming  tool 
to  clear  the  holder  when 
fed  in  enough  to  cut  its 
full  shape.  The  cutter 
thus  formed  has  no  clearance.  This,  however,  is  obtained 
by  the  simple  expedient  of  setting  the  cutter  farther  out. 
Grinding  a fly  cutter  thus  made  will  not  materially  change  its 
shape,  as  long  as  the  precaution  is  taken  of  grinding  it  on  its 
front  face  in  such  a way  that  the  face  remains  radial.  The 
cutter  should  be  of  sufficient  thickness  to  give  a radial  front 
face,  as  shown  in  the  illustration. 


Fig.  4. 


FORMED  CUTTERS. 

11.  For  milling  irregular  contours  on  repetition  work 
done  in  large  quantities,  formed  cutters  with  teeth  shaped 
to  conform  to  the  contour  required  are  in  universal  use. 


§27 


TOOLMAKING. 


11 


These  milling  cutters  are 
so  formed  that  they  can 
be  ground  on  the  face  of 
the  cutting  edges  without 
changing  the  shape  of  the 
contour.  This  form  can 
only  be  given  by  the  aid 
of  special  machinery  de- 
signed for  that  purpose 
and  not  usually  found  in 
a tool  room.  For  this 
reason,  it  is  cheaper,  as 
a general  rule,  to  have 
formed  cutters  made  to 
order  by  shops  making  a 
specialty  of  this  work. 

12.  Backing-Off 
Attachments.  — Should 
circumstances  render  it 
advisable  to  make  formed 
cutters  in  the  tool  room, 
an  engine  lathe  can  be 
converted  temporarily  in- 
to a backing-off  ma- 
chine. The  attachments 
required  will  not  in  the 
least  destroy  the  useful- 
ness of  the  lathe  as  a 
lathe,  as  will  become  ap- 
parent when  the  device 
is  studied.  For  attaching 
the  device,  a lathe  with  a 
compound  rest  must  be 
selected.  The  lathe  se- 
lected should  be  very 
stiff  and  of  ample  size; 
it  is  recommended  that  a 


C.  5.  III.— 34 


12 


TOOLMAKING. 


§27 


20-inch  lathe  be  used  in  preference  to  a smaller  one.  The 
larger  lathe  is  likely  to  be  much  stiffer,  which  is  essential  in 
order  to  do  good  work. 

The  backing-off  attachment  shown  in  Fig.  5 is  one  that  is 
quite  simple,  relatively  inexpensive,  adaptable  to  any  lathe 
having  a compound  rest,  and  will  do  excellent  work.  Its 
drawbacks  are  several  : First , the  amount  of  clearance  for 
a given  size  cutter,  i.  e.,  the  difference  in  the  distances  from 
the  center  of  the  cutter  to  the  front  edge  and  the  back  edge 
of  the  land,  cannot  be  changed,  being  governed  by  the  way 
the  cam  is  laid  out;  second,  the  shape  of  the  cam  determines 
the  number  of  cutting  edges,  which  cannot  be  changed 
without  making  a new  cam  ; third,  using  one  cam  only,  the 
amount  of  clearance  will  be  the  same,  irrespective  of  the 
diameter  of  the  cutter.  From  this  it  follows  that  a large 
cutter  will  have  a much  smaller  angle  of  relief  than  a small 
one.  This  will  be  referred  to  again  farther  on. 

13.  The  device  consists  essentially  of  a cam  a rigidly 
attached  to  a small  face  plate  in  any  convenient  manner.  A 
roller  b,  which  is  carried  by  a bracket  c rigidly  bolted  to  the 
lower  part  of  the  slide  rest,  engages  the  cam  a and  is  held 
against  it  by  a heavy  weight  attached  to  the  rope  d.  The 
cross  feed-screw  being  taken  out  of  the  cross  feed-slide,  the 
latter,  by  reason  of  the  roller  engaging  the  revolving  cam,  is 
moved  in  and  out  in  a manner  depending  on  the  shape  of 
the  cam.  The  compound  rest  is  swung  around  square  with 
the  bed,  and  the  forming  tool  e is  held  in  the  tool  post.  It 
is  fed  forwards  by  means  of  the  feed-screw  in  the  upper  part 
of  the  compound  rest.  The  cutter  that  is  to  be  backed  off 
is  clamped  to  a short,  stiff  arbor,  which  may  either  form 
part  of  the  cam,  or  be  fitted  to  the  live  spindle  and  driven 
by  a dog.  Before  backing  off,  the  cutter  must  be  serrated; 
it  is  then  clamped  on  the  arbor  in  such  a position  that  its 
cutting  faces  are  in  the  same  radial  planes  as  the  high  points 
of  the  cam.  This  is  most  readily  done  by  first  setting  the 
cam  by  eye  so  that  one  of  its  high  points  is  on  the  straight 
line  joining  the  center  of  the  lathe  spindle  and  the  center  of 


§27 


TOOLMAKING. 


13 


the  roller.  Then,  with  the  forming  tool  set  to  the  height  of 
the  lathe  center,  the  tool  is  run  forwards  until  it  nearly 
touches  the  cutter,  which  is  then  rotated  on  its  arbor  until 
a cutting  edge  is  in  the  same  plane  as  the  top  face  of  the 
forming  tool.  The  cutter  is  now  properly  set  and  is  then 
clamped. 


14.  A rather  simple  way  of  backing  off  milling  cutters 
was  made  public  by  Mr.  R.  D.  Morse  in  1899.  The  rig  used 


recommends  itself  for  its  simplicity  and  cheapness;  it  is 
open  to  only  one  objection:  as  the  cutting  faces  are  ground 
away,  the  shape  milled  by  the  cutter  changes  slightly.  The 
amount  of  this  change  is  quite  small,  however,  and  for  many 


14 


TOOLMAKING. 


§27 


classes  of  work  may  be  permissible.  The  device  consists  essen- 
tially of  a stud  a , Fig.  6,  securely  screwed  into  the  face  plate 
of  a lathe  near  its  periphery.  This  stud  is  turned  to  fit  the 
hole  of  the  cutter,  which  is  clamped  to  the  stud  by  the  nut 
shown.  A pawl  b,  movable  longitudinally  in  a rectangular 
slot  of  the  bridge  c , serves  to  keep  the  cutter  from  turning. 
The  pawl  is  kept  from  moving  by  the  setscrew  d.  A form- 
ing tool,  which  may  be  circular  as  shown  at  e , or  flat  as  was 
shown  in  connection  with  the  making  of  a fly  cutter,  is  held 
in  the  tool  post  of  the  lathe  and  fed  in  gradually  until  the 
tooth  is  formed.  After  one  tooth  is  formed,  as  the  tooth  f, 
the  pawl  b is  unlocked  and  slipped  back.  The  milling  cut- 
ter operated  on  is  rotated  one  notch  to  bring  another  tooth 
in  position,  the  pawl  is  slipped  forwards  and  locked,  the  cut- 
ter clamped  again  and  the  forming  tool  fed  in  once  more. 
This  is  repeated  until  each  tooth  has  been  backed  off.  It 
will  be  understood  that  the  milling  cutter  does  not  rotate  in 
respect  to  the  face  plate,  but  rotates  with  the  face  plate.  If 
a cutter  is  backed  off  in  this  device,  it  is  necessary  to  cut  the 
notches  slightly  wider  than  the  lands. 

15.  Laying  Out  Cams  for  Formed  Cutters. — Be- 
fore a cam  for  a backing-off  attachment  can  be  laid  out, 

several  factors  that  in- 
fluence its  design  must 
be  known.  These  are 
the  diameter  of  the  cam, 
the  diameter  of  the  cut- 
ter, the  number  of  teeth, 
and  the  angle  of  relief 
that  the  cutter  is  to 
have.  Of  these  factors, 
the  minimum  diameter 
of  the  cam  is  fixed  by 
the  design  of  the  lathe 
it  is  proposed  to  use.  In 
general,  the  cam  should 
made  as  small  as  these  considerations  permit,  since  there 


§ 27 


TOOLMAKING. 


15 


is  nothing  gained  by  making  it  large.  The  diameter  of  the 
cutter  and  the  number  of  teeth  being  known,  the  only 
factor  left  is  the  best  angle  of  relief.  For  wrought  iron, 
cast  iron,  and  steel,  it  may  be  made  about  8°;  for  brass, 
about  10°  to  12°.  In  order  that  there  may  be  no  misunder- 
standing about  the  term  “angle  of  relief,”  it  is  here  defined 
as  the  angle  f,  Fig.  7,  included  between  a line  perpendicular 
to  a radial  line  and  tangent  to  the  cutting  edge,  as  a b , and 
a line  tangent  to  the  curved  surface  of  the  tooth  at  the 
intersection  of  the  radial  line  o e and  the  line  a b perpendic- 
ular to  it,  as  c d. 

16.  The  preliminary  data  having  been  determined,  the 
cam  outline  is  laid  off  as  follows:  Referring  to  Fig.  8,  draw 


a circle  having  a diameter  equal  to  that  of  the  cam.  Divide 
this  circle  into  a number  of  equal  divisions  equal  to  the 
number  of  teeth.  From  one  of  these  points  draw  a radial 
line,  as  a o.  Next,  multiply  the  angle  of  relief  determined 
upon  by  the  outside  diameter  of  the  cutter  and  divide  the 


16 


TOOLMAKING. 


§27 


product  by  the  outside  diameter  of  the  cam.  The  quotient 
will  be  the  angle  ;r,  which  the  line  a b is  to  make  with  a o. 
Thus,  if  the  angle  of  relief  is  to  be  12°,  and  if  the  cutter 
is  3 inches  in  diameter  and  the  cam  9 inches,  the  angle  that 

12  X 3 

a b is  to  make  with  a o is  — — — = 4°.  The  line  a b having 

been  drawn,  draw  a circle  about  o as  a center  and  tangent 
to  the  line  a b.  With  half  the  outside  diameter  of  the  cam 
as  a radius,  and  from  the  points  of  division  on  the  outer 
circle,  describe  arcs  intersecting  the  circle  tangent  to  a b. 
With  the  points  of  intersection  as  centers  and  the  same 
radius,  describe  arcs,  as  a c.  Next,  with  a radius  equal  to 
about  one-fifth  the  distance  between  adjoining  divisions  on 
the  outer  circle  and  from  the  points  of  division,  describe 
arcs  intersecting  those  previously  drawn.  Join  the  points  of 
intersection  and  the  points  of  division  on  the  outer  circle  by 
straight  lines,  as  a e.  This  will  complete  the  cam  outline. 

17.  Making  a Cam  for  Formed  Cutters. — There  is 
a variety  of  ways  in  which  the  cam  may  be  made.  One  way 


Fig.  9. 

that  can  be  recommended,  on  account  of  the  accuracy  that 
can  be  obtained  by  it  at  slight  expense,  is  shown  in  Fig.  9. 
In  the  illustration,  a is  the  cam;  b and  c are  filing  templets 
secured  and  held  in  proper  position  by  the  plugs  d and  c. 


§ 27 


TOOLMAKING. 


17 


The  outer  ends  of  the  two  filing  templets  are  shaped  to  the 
proper  cam  outline  and  are  wide  enough  to  cover  one  sec- 
tion. They  are  hardened  at  the  ends  as  hard  as  possible, 
and,  when  placed  in  position,  the  cam  is  worked  down  to 
them.  The  plug  e is  then  withdrawn  and  the  templets  re- 
volved  to  the  next  hole,  as  f,  when  the  plug  is  inserted 
again.  This  is  repeated  until  the  cam  is  completed. 

The  first  step  in  making  the  cam  and  templet  is  to  bore, 
turn,  and  face  the  cam-blank,  which  may  be  made  of  cast 
iron.  While  still  on  the  mandrel  on  which  it  has  been  turned, 
put  it  in  the  milling  machine  and  divide  the  periphery  by 
fine  scriber  lines,  scribed  preferably  on  the  face,  into  the 
proper  number  of  equal  divisions,  using  the  index  head  for 
the  purpose.  Make  a temporary  drilling  jig  shaped  about 
like  the  templets.  Bore  a hole  to  fit  the  mandrel  closely  and 
bevel  some  part  near  the  end  of  the  jig.  Mark  a fine  radial 
line  on  this  bevel  and  drill  a small  hole,  say  about  ^ inch  in 
diameter,  somewhere  on  the  jig  at  a distance  from  the  cen- 
ter of  the  large  hole  equal  to  about  four-fifths  the  radius  of 
the  cam.  Then,  by  placing  this  drill  jig  on  the  mandrel  and 
making  the  line  marked  on  it  coincide  successively  with  the 
division  lines  near  the  periphery  of  the  cam,  the  hole  in  the 
drilling  jig  can  be  transferred  to  the  cam  by  drilling,  thus 
drilling  a row  of  holes  equidistant  from  the  center  and 
equally  spaced.  Next,  on  a piece  of  sheet  steel,  by  the 
method  previously  given,  lay  out  the  cam  outline  for  one 
section.  Carefully  file  to  the  line;  then  bore  the  hole  to  fit 
the  plug  d (or  the  mandrel,  if  the  work  of  making  the  plug 
is  to  be  saved),  and  place  it  on  the  plug,  clamping  it  to  the 
cam.  Drill  the  hole  intended  for  the  plug  e through  the 
templet,  thus  using  the  cam  as  a jig;  then  harden  its  end 
and  from  it  make  an  exact  duplicate  by  pushing  plugs  d 
and  e through  both  templets  and  then  filing  the  second  one 
to  the  first,  or  hardened,  templet.  Harden  the  second  one; 
put  both  in  place  and  then  file  the  cam  to  them. 

18.  Forming  Tool. — -The  forming  tool  should 
always  be  set  so  that  its  top  face  is  radial,  as  indicated  in 


18 


TOOLMAKING. 


§27 


Fig.  10  by  the  dotted  line.  If  thus  set,  it  will  reproduce 
exactly  the  shape  given  to  its  cutting  edge.  The  forming 
tool  requires  considerable  clearance  on  account  , of  the  cut- 
ting being  done  on  an  arc  eccentric  in  respect  to  the  axis  of 
the  milling  cutter.  The  angle  included  between  the  face  of 
the  forming  tool  and  its  top  can  be  found  by  adding  10° 
to  the  angle  of  relief  of  the  cutter  and  subtracting  the  sum 


from  90°.  Thus,  if  the  angle  of  relief  is  8°,  the  angle 
Fig.  10,  should  be  90°  — (8°  + 10°)  = 72°.  If  the  forming 
tool  is  given  the  angle  calculated  by  the  method  just  given, 
it  will  have  a cutting  clearance  of  10°,  which  is  considered 
ample. 

When  making  a forming  tool,  it  must  not  be  assumed  that 
the  form  can  be  planed  or  milled  with  a tool  having  exactly 


27 


TOOLMAKING. 


19 


the  shape  it  is  desired  to  produce.  That  this  cannot  be  done 
is  shown  in  Fig.  10.  The  forming  tool  there  shown  is  of 
such  simple  form  that  it  clearly  exhibits  the  difference  in 
shape.  Let  a b be  the  depth  of  the  form  of  the  forming 
tool  and  cd  its  width.  Then,  the  tool  that  could  plane 
this  shape  must  have  a depth  a b\  while  its  width  would  be 
the  same  as  c d.  Now,  in  the  right-angled  triangle  a b b' , the 
side  a b'  adjoining  the  right  angle  must  be  shorter  than  the 
hypotenuse  a b.  Transferring  the  distance  a b'  to  the  plan 
view,  and  laying  off  a'  b — a //,  we  get  c a' d as  the  shape  of 
the  form  at  a right  angle  to  be.  In  other  words,  the  pla- 
ning tool  or  milling  cutter  used  to  produce  a form  as  cad 
must  have  the  shape  c a' d,  which  differs  somewhat  from 
the  shape  desired.  This  difference  in  shape  will  vary  with 
the  angle  d. 

19.  Theoretically,  it  is  possible  to  lay  out,  by  the  prin- 
ciples of  descriptive  geometry,  the  correct  shape  of  planing 
tool  required  to  cut  the  form;  it  is  not  such  an  easy  mat- 
ter, however,  to  transfer  this  layout  to  steel,  owing  to  the 
differences  in  shape  being  very  small.  Hence,  in  practice, 
forming  tools  are  made  in  a different  manner. 

The  forming  tool  having  been  planed  and  squared  all  over, 
the  form  is  roughed  out  and  the  cutting  edge  filed  to  cor- 
rect shape,  filing  at  a right  angle  to  the  top  surface.  The 
tool  is  then  placed  in  the  vise  of  a milling  machine  or  shaper 
at  the  proper  inclination  to  give  the  required  clearance,  and, 
with  a pointed  tool  or  narrow  milling  cutter,  the  clearance 
is  cut  in  successive  steps,  using  the  extreme  cutting  edge  as 
a guide  for  setting  the  cutting  tool.  By  careful  manipula- 
tion, using  a pointed  tool  or  narrow  cutter,  the  forming  tool 
can  be  cut  very  close  indeed  to  the  required  form  and  will 
then  require  very  little  filing.  If  thus  made,  the  cross- 
section  of  the  form  will  be  the  same  throughout  the  depth 
of  the  forming  tool;  in  consequence  of  this,  the  tool  can  be 
ground  on  its  top  surface  without  changing  its  shape,  pro- 
vided the  precaution  is  taken  of  always  grinding  square 
across  and  without  changing  the  angle  d. 


20 


TOOLMAKING. 


§27 


WORM-WHEEL  HOBS. 

20.  Designing  tlie  Hob. — The  hob  for  cutting  the 
teeth  of  worm-wheels  is  a special  kind  of  a milling  cutter. 
It  is  practically  a duplicate  of  the  worm,  except  that  it  is 
made  slightly  larger  in  diameter.  It  is  serrated  to  form 
cutting  edges,  as  shown  in  Fig.  11.  The  grooves  or  slots 
are  sunk  in  deep  enough  to  go  below  the  bottom  of  the 
thread,  as  shown. 


e 


'y-ZSf-J 

MM  \ / 


Fig.  11. 


Most  worms  and  worm-wheels  are  made  in  accordance 
with  the  involute  system  of  gearing  adopted  by  the 
Browne  & Sharpe  Manufacturing  Company,  the  teeth  of 
the  worm  having  the  same  shape  as  the  teeth  of  a rack  of  the 
same  pitch.  The  angle  included  between  the  sides  of  the 
teeth  is  29°,  or  each  side  makes  an  angle  of  14|-°  with  a plane 
perpendicular  to  the  axis  of  the  hob.  In  this  system,  the 
whole  depth  of  the  tooth  (or  space)  for  the  worm  is  found 
by  multiplying  .G8G6  by  the  pitch;  by  pitch  is  here  meant 
the  distance  between  corresponding  points  of  adjoining 
teeth,  as  the  distance  /,  Fig.  11.  The  word  pitch  as  here 
used  should  not  be  confounded  with  the  term  lead , which, 
when  used  in  reference  to  a worm,  implies  the  distance 
that  one  thread  advances  in  a complete  revolution.  For  a 
double-threaded  worm,  the  pitch  will  be  one-half  the  lead, 
and,  for  a triple-threaded  worm,  it  will  be  one-third  the 
lead.  Knowing  the  outside  diameter  of  the  worm  and  the 


§27 


TOOLMAKING. 


21 


pitch,  the  diameter  across  the  bottom  of  the  spaces,  or  inside 
diameter,  is  equal  to  the  outside  diameter  diminished  by 
twice  the  whole  depth  of  worm-thread.  Some  toolmakers 
make  the  inside  diameter  of  the  hob  equal  to  the  inside 
diameter  of  the  worm,  while  others  make  it  somewhat  less. 
The  outside  diameter  of  the  hob  is  found  by  adding  one- 
tenth  the  pitch  to  the  outside  diameter  of  the  worm. 
Thus,  if  the  worm  is  3 inches  outside  diameter  and  .7  inch 
pitch,  the  inside  diameter  of  the  worm  (and  of  the  hob)  is 
3 — 2 X .G866  X .7  = 2.04  inches.  The  outside  diameter  of 
the  hob  will  be  .1  X .7  + 3 = 3.07  inches. 

21.  Hob-Forming  Tool. — The  tool  for  threading  the 
hob  and  worm  should  include  an  angle  of  29°  and  be  cut  off 
square  across  until  its  width  at  the  end  is  equal  to  .31  times 
the  pitch.  For  the  hob  under  discussion,  the  end  of  the  tool 
should  be  .31  X .7  = .217  inch  wide.  To  find  the  side  clear- 
ance required  for  the  tool,  draw  a line,  as  ab  in  Fig.  11  ( a ), 
equal  in  length  to  the  circumference  of  a circle  having  a 
diameter  equal  to  the  inside  diameter  of  the  worm.  At  the 
one  end  erect  a perpendicular  be,  equal  in  length  to  the 
pitch.  Join  a and  c by  a straight  line.  At  any  convenient 
point  on  the  line  ab,  erect  a perpendicular  de,  and,  from  its 
point  of  intersection  with  the  line  ac,  draw  lines  fg  and  fh 
at  an  angle  of  10°  to  a c.  Then,  the  angles  e fg  and  d fh 
are  the  angles  that  the  sides  of  the  thread  tool  must  make 
with  a surface  on  which  the  tool  is  resting  in  the  same 
position  it  will  occupy  in  the  lathe.  For  a right-handed 
worm,  the  angle  e fg  is  that  of  the  left-hand  side  of  the  tool, 
looking  on  top  of  the  tool  from  the 
shank  toward  its  cutting  end.  For  a 
left-handed  worm,  the  angle  e fg  be- 
longs to  the  right-hand  side  of  the  tool. 

22.  A 29°  angle  may  be  laid  out 
by  the  following  construction,  taken 
from  Brown  & Sharpe’s  treatise  on 
“Gearing.”  In  a circle  of  any  con- 
venient size,  draw  any  diameter,  as  a b, 


22 


TOOLMAKING. 


27 


Fig.  12.  From  a , with  a radius  equal  to  one-fourth  the 
diameter,  describe  arcs  intersecting  the  circumference  of  the 
circle  at  c and  d.  Draw  the  lines  cb  and  d b.  The  angle 
included  between  these  two  lines  is  29°,  very  nearly.  The 
actual  angle  given  by  this  construction  is  28°  58';  this  is 
close  enough  for  the  purpose  to  call  it  29°. 


23.  Width  and  Number  of  Slots. — The  width  of  the 
round  end  of  the  cutter  used  for  serrating  the  hob  may  be 
about  .17  X pitch  -j-  .12  inch.  Thus,  for  a hob  having  a pitch 
of  .7  inch,  the  cutter  may  be  about  .17  X .7  + .12  = .239  inch, 
say  \ inch  wide.  The  number  of  slots  should  be  such  that 
the  width  of  land  at  the  bottom  of  the  slots  is  about  equal 
to  the  depth  of  the  thread  plus  .12  inch.  To  find  the  num- 
ber of  slots,  divide  the  circumference  corresponding  to  the 
inside  diameter  of  the  hob  by  the  depth  of  the  worm-thread 
increased  by  .12  inch  plus  the  width  of  the  cutter.  Thus, 
taking  a pitch  of  .7  inch,  the  depth  of  the  thread  of  a worm 
is  .6866  X .7  = .48  inch.  Using  a cutter  \ inch  wide  on  the 
end,  the  number  of  slots  will  be,  for  an  inside  diameter  of 
2.04  inches, 


2.04  X 3.1416 
.48  -J-  .12  — J-  .25 


= 7 slots. 


The  construction  of  a hob  is  influenced  by  the  work  to  be 
done  and  the  manner  of  doing  it.  If  the  hob  is  to  be  used 
in  an  automatic  hobbing  machine  or  gear-cutter,  where  the 
blank  is  mechanically  rotated,  the  number  of  cutting  edges 
may  be  reduced.  If  the  blank  is  gashed  and  the  hob  de- 
pended on  for  rotating  the  blank,  a greater  number  of  teeth 
will  be  necessary,  so  that  at  least  two  teeth  may  always  be 
in  contact  with  the  blank.  Hobs  work  best  when  the  grooves 
are  spirals  at  right  angles  to  the  thread,  in  place  of  parallel 
to  the  axis  of  the  hob;  as  in  the  former  case,  each  tooth  has 
two  equal  cutting  edges  instead  of  one  acute  edge  and  One 
obtuse  edge.  When  the  grooves  are  parallel  to  the  axis  of 
the  work,  they  should  be  so  cut  that  the  cutting  faces  of 
the  teeth  in  the  center  of  the  hob  are  radial.  Hobs  are 
sometimes  hardened  without  backing  off.  This  will  answer 


TOOLMAKING. 


23 


§ 27 

in  the  case  of  a hob  intended  for  cutting  only  one  or  two 
gears,  but  if  the  hob  is  to  do  much  work,  it  should  be  backed 
off  on  all  cutting  edges.  For  large  worm-wheels,  the  body 
of  the  hob  is  sometimes  made  of  cast  iron  or  machinery  steel 
and  provided  with  inserted  cutters  or  teeth.  A hob  must 
be  at  least  as  long  as  the  portion  of  the  worm  that  engages 
any  of  the  teeth  of  the  worm-wheel.  In  some  cases  where 
the  worm-wheel  is  to  be  cut  in  an  automatic  machine,  a 
short  hob  is  made  for  roughing  and  a longer  one  for  finish- 
ing. The  teeth  of  the  hob  may  be  plugs  inserted  and  fast- 
ened with  setscrews.  The  teeth  are  sharpened  by  grinding 
in  the  slots  with  a narrow  and  rather  coarse  emery  wheel. 


DIVIDING  CIRCLES  AND  LINES. 


DIVISION  OF  THE  CIRCLE. 

24.  The  toolmaker  is  frequently  required  to  divide  a 
circle  into  a given  number  of  integral  divisions.  This 
may  necessitate  the  making  of  an  original  index  plate,  with 
holes  equidistant  from  the  center  and  each  other  and  pier- 
cing the  index  plate  at  a right  angle  to  its  surface;  or  it 
may  require  the  spacing  of  notches  equidistant  around  the 
periphery,  or  the  dividing  of  the  rim  by  lines  or  dots  into 
equidistant  divisions. 

25.  There  are  quite  a number  of  ways  in  which  a circle 
may  be  divided  mechanically;  some  of  these  require  the  use 
of  scientific  apparatus  not  to  be  found  in  tool  rooms,  while 
others  require  nothing  beyond  the  facilities  ordinarily  at  the 
command  of  the  toolmaker.  Some  of  these  latter ’methods 
are  here  explained;  each  one  of  them  has  actually  been  used 
and  proved  satisfactory  when  reasonable  skill  was  displayed 
by  the  workman.  The  ultimate  accuracy  attainable  by 
either  one  of  the  methods  given  largely  depends  on  the  skill 
and  patience  of  the  toolmaker;  neither  one  of  the  methods 
given  is  here  recommended  as  in  general  superior  to  the 
others.  Hence,  the  choice  of  method  must  be  governed  by 


24 


TOOLMAKING. 


§27 


the  circumstances  of  each  case,  selecting  that  method  which  is 
best  adapted  to  the  nature  of  the  job  and  the  facilities  at  the 
command  of  the  toolmaker. 


DIVIDING  BY  MECHANICAL  CORRECTION  OF  ERRORS. 

26.  In  Fig.  13,  one  way  of  accurately  dividing  a jig  or 
index  plate  into  a given  number  of  divisions  is  shown.  This 
method  was  first  made  public  by  Mr.  Wm.  Baxter  in  the 
columns  of  the  “American  Machinist.”  While  there  is 


little  doubt  that  by  its  use  it  is  possible  to  space  holes 
equidistant  from  the  center  and  each  other  within  an  uncom- 
monly small  limit  of  error  if  sufficient  patience  is  exercised, 
it  cannot  be  claimed  for  it  that  it  will  also  accurately  locate 
the  holes  on  a circle  of  a given  predetermined  diameter. 
Hence,  if  great  accuracy  in  the  diameter  of  the  circle  on 
which  the  holes  are  located  is  an  essential  condition,  the 
method  is  not  applicable. 


TOOLMAKING. 


25 


§27 

27.  In  the  illustration,  let  a be  the  jig  that  is  to  be 
pierced  to  receive  hardened  steel  bushings.  Make  a ring  b 
of  the  same  material  and  approximately  of  the  same  thick- 
ness as  the  flange  of  a , fitting  the  inside  of  the  ring  carefully 
to  the  projecting  rim  of  a.  On  the  surface  of  the  ring  b , the 
centers  are  laid  out  as  carefully  as  possible,  spacing  them 
with  a pair  of  dividers  on  a scribed  circle  of  the  given  diam- 
eter. The  ring  and  jig  is  then  clamped  together  and  the 
holes  are  drilled  through  both.  After  the  holes  have  been 
drilled,  a taper  reamer  and  two  pins  of  exactly  the  same 
taper  are  needed.  If  the  holes  have  been  drilled  with  a 
£-inch  drill,  a reamer  about  5 inches  long  on  "the  cutting 
edge  and  tapering  from  a scant  J inch  at  the  small  end  to 
about  § inch  at  the  large  end,  will  usually  be  about  right. 

After  drilling,  if  the  ring  b be  shifted  one  hole,  it  will  be 
found  that  the  other  holes  do  not  match.  To  make  them 
match,  proceed  as  follows:  Place  the  ring  so  that  one  pair 
of  holes  fairly  matches  and  clamp  jig  and  ring  together. 
Ream  out  this  pair  of  holes  until  the  reamer  cuts  through  b 
and  just  enters  a.  Drive  one  of  the  taper  pins  lightly 
into  this  hole.  Ream  out  a hole  opposite  the  first  one  and 
insert  the  other  pin.  These  two  pins  prevent  any  shifting 
of  the  ring  on  the  jig  in  the  subsequent  operations.  Now, 
ream  out  all  the  holes,  running  the  reamer  in  to  the  same 
depth  in  each  one.  If  it  should  happen  that  two  correspond- 
ing holes  are  so  far  out  of  line  as  to  require  the  reamer  to 
be  run  in  deeper  than  in  the  first  hole  in  order  to  cut  all 
around  the  edge  of  the  hole  in  the  jig,  ream  out  until  this  is 
accomplished  and  then  go  over  the  holes  previously  reamed 
and  ream  them  out  to  the  same  size  as  the  last  hole.  All 
holes  having  been  reamed,  take  off  the  clamps  and  take  out 
the  taper  pins;  shift  the  ring  b one  hole  ahead,  match  the 
holes,  clamp  the  ring  and  jig  together,  ream  out  an  opposite 
pair  of  corresponding  holes,  insert  the  pins,  and  reream  all 
the  holes.  Shift  one  hole  ahead  again  and  continue  this 
until  all  holes  match  in  the  ring  and  jig.  If  the  holes  have 
been  located  fairly  accurate  at  first,  it  is  rarely  necessary 
to  repeat  the  operation  more  than  six  or  eight  times  to  bring 


TOOLMAKING. 


§27 


26 

them  in  line.  If  the  holes  should  match  before  the  reamer 
has  cut  all  the  way  through  the  jig,  the  operation  of  shift- 
ing one  hole  ahead  and  rereaming  should  be  continued  until 
it  does. 

It  is  not  advisable  to  run  the  reamer  all  the  way  through 
in  one  position  of  the  ring  and  jig,  even  though  the  holes 
match  perfectly;  it  is  much  better  to  remove  only  a little 
metal  from  each  hole  and  then  shift  the  ring  again.  If  it  is 
desired  that  the  holes  should  be  cylindrical  instead  of  conical, 
the  large  end  of  the  taper  reamer  may  be  made  parallel 
beyond  the  taper  and  then  run  through  all  the  way,  remov- 
ing only  a small  amount  of  metal  from  each  hole  and  then 
shifting  again.  This  job  may  be  done  most  conveniently  in 
a drill  press.  When  finished,  both  ring  and  jig  will  be  dupli- 
cates of  each  other  and  both  will  be  correct;  the  ring  may 
afterwards  be  used  as  an  original  index  plate,  or  may  be  con- 
verted into  a duplicate  jig.  The  accuracy  that  may  be 
obtained  by  this  method  is  believed  to  be  greater  with  a 
relatively  thin  ring  and  jig  than  with  thicker  ones,  and 
depends  more  on  patience  than  on  skill. 


DIVIDING  BY  CONTACT  MEASUREMENTS. 

28.  Another  method  that  differs  considerably  from  the 
previous  one  is  shown  in  Fig.  14.  By  this  method,  holes  can 
be  located  very  closely  within  a given  distance  from  the  cen- 
ter; it  is  believed  that  after  holes  bored  by  this  method 
are  corrected  again  by  that  shown  in  Fig.  13,  the  holes  can 
be  spaced  within  a practically  insensible  amount  of  error 
and  thus  perhaps  the  closest  approximation  to  true  spacing 
that  is  possible  by  purely  mechanical  means  may  be  obtained. 
In  the  illustration,  let  a be  the  work  that  is  to  be  pierced  by 
holes  perpendicular  to  its  surface.  Let  a'  be  a projection 
intended  to  center  the  jig  on  the  work.  Then,  a circle  of 
approximately  correct  diameter  having  been  scribed  cen- 
trally on  a , divide  this  circle  with  dividers  into  the  required 
number  of  divisions,  and  drill  and  tap  at  the  points  of  divi- 
sion for  a small  machine  screw  of  convenient  size.  Make  a 


TOOLMAKING. 


27 


§ 27 


number  of  steel  bushings  or  buttons  having  an  inside  diameter 
about  -J  inch  larger  than  the  diameter  of  the  machine  screw 
and  an  outside  diameter  of  any  convenient  size.  Assemble 


these  bushings  on  a long  arbor  and  grind  them  truly  round 
and  to  the  same  diameter.  Finish  the  outside  by  lapping 
carefully  to  insure  that  all  bushings  are  the  same  diam- 
eter. As  far  as  the  diameter  is  concerned,  it  need  not  be 
any  accurate  size;  the  only  thing  essential  is  that  all  bush- 
ings have  the  same  diameter. 

The  height  of  the  bushings  is  immaterial;  it  is  necessary, 
however,  that  the  top  and  bottom  surfaces  of  each  bushing 
shall  be  parallel  and  in  planes  at  a right  angle  to  the  axis  of 
the  bushing.  The  inside  of  the  bushings  does  not  need  to 
be  finished  to  any  extent.  The  bushings  having  been  made, 
caliper  their  size  with  a micrometer.  Subtract  this  diameter 
from  the  diameter  of  the  circle  on  which  the  holes  are  to  be 
located ; the  remainder  will  be  the  outside  diameter  of  a nar- 
row ledge,  as  b , that  is  turned  centrally  with  a'.  Evidently, 


C.  S.  III.— 35 


28 


TOOLMAKING. 


§27 


if  the  buttons  are  in  contact  with  the  ledge,  their  distance 
from  the  center  of  the  button  to  the  center  of  the  jig  will 
be  equal.  Fasten  the  buttons  c,  c by  means  , of  machine 
screws,  placing  a smooth  washer  that  has  parallel  sides 
between  the  head  of  the  screw  and  each  button.  Then, 
each  button  being  in  contact  with  the  ledge  b , adjust  but- 
tons about  90°  apart  until,  by  calipering  over  their  cylindrical 
surface,  they  are  shown  to  be  spaced  equidistant.  Then, 
adjust  the  buttons  located  between  those  just  adjusted  until 
calipering  shows  all  the  buttons  to  be  equidistant. 

After  each  adjustment  is  made,  tighten  the  screws  suffi- 
ciently to  prevent  any  accidental  shifting  of  the  button. 
The  buttons  being  properly  located,  mount  the  jig  on  a true 
running  face  plate  and  true  it  until  one  of  the  buttons  runs 
true,  as  shown  by  a sensitive  indicator.  Remove  this  button 
and  bore  the  hole  carefully.  In  the  same  manner,  bore  all 
the  other  holes. 

In  this  method,  the  errors  that  preclude  absolute  accuracy 
are  chiefly  the  error  made  in  locating  the  buttons  and  the 
error  in  truing  up  by  them.  However,  with  careful  workman- 
ship and  a fairly  sensitive  sense  of  touch,  a remarkable  de- 
gree of  accuracy  can  be  obtained;  if  the  spacing  is  to  be  still 
more  accurate,  follow  by  the  method  shown  in  connection 
with  Fig.  13. 


DIVIDING  BY  CHORD  MEASUREMENTS. 

29.  Fig.  15  shows  a method  of  originating  an  accurate 
index  plate  that  was  devised  and  successfully  used  by  the 
writer.  While,  for  practical  reasons,  it  is  limited  in  its 
application,  there  are  undoubtedly  many  jobs  on  which  this 
method  can  be  used  with  good  results,  as  far  as  accuracy 
and  low  first  cost  are  concerned.  As  shown  in  the  figure, 
there  are  a number  of  bars,  as  a , a , connected  together  at 
their  ends  by  concentric  hardened  steel  bushings  b,  b,  fitting 
closely  in  the  holes  in  the  bars.  A cylindrical  projection  on 
the  work  is  carefully  turned  down  centrally  with  the  axis  of 
the  plate  until  it  fils  the  inside  of  the  bars  closely.  Then, 


§27 


TOOLMAKING. 


29 


if  all  bars  have  the  same  center-to-center  distance  between 
their  holes,  and  if  the  holes  in  each  bar  occupy  the  same 
relative  position  in  regard  to  the  inside  surface  of  the  bars, 
holes  drilled  and  reamed  through  the  connecting  bushings 
after  clamping  the  device  to  the  work  must  be  equidistant 
from  each  other  and  equidistant  from  the  center  of  the 
work.  The  degree  of  accuracy  attainable  by  this  device,  as 


far  as  the  division  of  the  circle  is  concerned,  depends  on  the 
limit  of  variation  within  which  the  bars  can  be  made  alike  in 
their  essential  dimensions. 

A temporary  jig  may  be  constructed  for  the  bars;  after 
drilling  the  holes  in  all  the  bars,  use  a rose  reamer  that  fits 
very  closely  into  the  bushings  of  the  jig  and  run  it  through 
while  flooded  with  oil.  The  difference  in  the  center-to-cen- 
ter  distance  of  the  various  bars  may  thus  be  well  kept  within 
a limit  of  .0001  inch,  and  if  the  work  is  done  at  all  carefully, 
this  limit  of  variation  need  not  be  exceeded  in  the  relative 
positions  of  the  holes  in  respect  to  the  edge  intended  to  bear 
against  the  cylindrical  central  projection  of  the  work.  The 


30 


TOOLMAKING. 


§27 

limit  of  accuracy  within  which  the  holes  can  be  located  on 
a circle  of  a given  diameter  is  dependent  primarily  on  the 
degree  of  accuracy  within  which  the  center-to-center  dis- 
tance of  the  holes  in  the  bars  agrees  with  the  calculated 
distance.  A straight  line  drawn  between  the  centers  of  the 
holes  of  each  bar  is  the  chord  of  a circle.  By  geometry,  the 
chord  of  a circle  is  equal  to  twice  the  sine  of  half  the  angle 
included  between  the  lines  drawn  from  the  center  of  the 
circle  to  the  extremities  of  the  chord.  Then,  to  find  the 
center-to-center  distance  of  the  holes  in  the  bars  required 
in  order  that  the  centers  will  lay  on  a circle  of  a given 
diameter: 

Rule. — Divide  360  by  twice  the  number  of  divisions  into 
which  the  circle  is  to  be  divided.  From  a table  of  natural 
sines , take  the  sine  corresponding  to  this  angle  and  multiply  it 
by  the  diameter  of  the  circle. 

To  prevent  any  mistake  in  assembling,  it  is  well  to  finish 
only  one  side  and  edge  of  the  bars  by  planing.  Then,  insert 
all  bars  the  same  way  in  the  jig,  with  the  planed  edge  against 
the  stops  and  the  planed  side  down;  finally  assemble  with 
the  planed  edge  inside  and  the  planed  side  down.  The  sides 
of  the  bars  should  be  fairly  parallel ; the  finished  edge  of 
each  bar  should  be  scraped  to  a straight  edge. 


DIVIDING  BY  ASSEMBLY  OF  EQUAL  PIECES. 

30.  While  most  index  plates  are  provided  with  correctly 
spaced  holes  that  receive  an  axially  movable  index  pin,  it 
may  also  be  made  with  notches  or  similar  spaces  that  receive 
a latch  of  suitable  form.  Such  an  index  plate  is  shown  in 
Fig.  16.  It  was  first  employed  in  connection  with  some 
part  of  the  Thorne  typesetting  machine,  where  a great 
accuracy  of  division  was  required.  As  shown  in  the  figure, 
the  circle  is  subdivided  into  exactly  equal  divisions  by  pla- 
cing circular  disks,  equal  in  number  to  the  number  of  divi- 
sions required,  in  contact  with  one  another  and  also  in  contact 
with  a central  circular  projection  on  the  index  plate.  The 


§27 


TOOLMAKING. 


31 


index  latch  pin  is  then  made  to  suit  the  approximately  tri- 
angular space  between  adjacent  disks. 

To  make  an  index  plate  in  this  manner,  make  the  disks 
truly  circular  and  of  exactly  the  same  diameter  by  mounting 
as  many  as  possible,  preferably  the  whole  lot  if  circum- 
stances permit,  on  an  arbor;  grind  them  true  and  then  finish 


by  lapping  as  if  it  were  a plug  gauge.  The  screw  holes  hav- 
ing been  drilled  and  tapped  in  the  body  of  the  plate,  by  care- 
ful grinding  reduce  the  diameter  of  the  central  projection 
until  all  disks  will  touch  the  projection  and  one  another.  If 
great  accuracy  is  required,  the  central  projection  must  be 
ground  while  the  index  plate  is  in  its  proper  place.  This 
will  then  insure  that  it  is  central  with  the  axis  around  which 
it  rotates.  Great  care  is  required  not  to  grind  the  projec- 
tion too  small;  it  should  be  remembered  that  any  reduction 
in  its  diameter  means  that  the  circumference  is  shortened 
more  than  three  times  that  amount. 


32 


TOOLMAKING. 


§27 


DIVIDING  BY  CORRECTING  THE  ACCUMULATED  ERROR. 

31.  Fig.  17  illustrates  a method  of  dividing  a circle  that 
differs  entirely  from  any  of  those  previously  shown.  This 


Fig.  17. 


method  is  based  on  the  principle  that  when  successive  equal 
measurements  are  made,  the  final  error  will  be  the  product 


27 


TOOLMAKING. 


33 


of  the  error  of  each  individual  measurement  and  the  num- 
ber of  measurements.  Referring  to  Fig.  17,  a and  b are  two 
movable  arms  free  to  rotate  about  a central  cylindrical  plug  c , 
which  is  closely  fitted  to  a central  hole  in  the  work  d.  The 
angular  distance  between  the  arms  is  adjustable  by  means  of 
the  screw  e , made  with  a very  fine  pitch  of  thread.  A locknut  / 
placed  on  the  screw  e prevents  any  motion  of  the  arms 
after  adjustment.  Each  arm  is  pierced  with  a hole  that 
receives  hardened  steel  bushings  these  bushings  must 

be  exactly  the  same  distance  from  the  center  of  rotation  of 
the  arms,  and,  at  the  same  time,  their  distance  from  the 
center  must  be  equal  to  the  radius  of  the  circle  on  which  the 
holes  in  the  work  are  to  be  located.  The  bushings  are  made 
a nice  fit  in  the  arms;  the  hole  through  the  bushings  must 
be  exactly  concentric  with  their  outside. 

To  use  this  device,  the  center-to-center  distance  between 
the  holes  is  first  calculated  by  the  rule  given  in  Art.  29 ; 
plugs  are  then  inserted  in  the  bushing  holes,  and,  by  measur- 
ing over  them  or  between  them  with  a vernier  caliper  or 
micrometer,  the  center-to-center  distance  of  the  holes  in  the 
arms  is  adjusted  by  means  of  the  screw  e to  coincide  as  closely 
as  circumstances  permit  with  the  calculated  distance.  The 
bushings  are  then  inserted  and  one  hole  is  drilled  and  reamed 
through  the  work.  A closely  fitting  plug  is  pushed  through 
the  bushing  into  the  hole  just  reamed  and  the  second  hole 
is  drilled  and  reamed.  The  plug  is  now  withdrawn  and  the 
device  shifted  until  the  plug  can  be  inserted  into  the  last 
hole.  Another  hole  is  now  put  through  the  work  and  this 
operation  is  continued  until  all  holes  have  been  drilled.  It 
will  now  be  usually  found  that  the  center-to-center  distance 
between  the  last  hole  and  the  hole  first  drilled  differs  from 
the  center-to-center  distance  of  the  other  holes.  If  it  is  less, 
it  shows  that  the  arms  are  too  far  apart;  if  it  is  more,  they 
are  too  close  together.  Readjust  the  arms,  remembering 
that  the  error  has  been  multiplied;  substitute  new  bushings 
with  a larger  hole  and  reream  all  the  holes.  Continue  until 
the  center-to-center  distance  between  the  first  and  the  last 
hole  is  equal  to  that  of  all  the  other  holes. 


34 


TOOLMAKING. 


§27 

32.  The  device  shown  may  be  varied  to  suit  circum- 
stances. Thus,  it  may  readily  be  adapted  for  drilling  radial 
holes  equally  spaced  around  the  periphery;  or  it  maybe 
used  for  graduating  the  face  or  the  periphery,  substituting 
a slide  carrying  a marking  point  for  the  bushing  in  one  arm 
and  placing  a microscope  with  cross-hairs  in  the  place  of  the 
other  bushing.  In  that  case,  a suitable  clamping  device 
must,  of  course,  be  added.  Knowing  the  principles  involved, 
numerous  modifications  will  suggest  themselves  upon  reflec- 
tion. 


DIVISION  OF  LINES. 


MECHANICAL  DIVISION. 

33.  The  most  familiar  and  most  common  form  in  which 
this  problem  presents  itself  to  the  toolmaker  is  the  equi- 
distant spacing  of  holes  that  are  located  on  a straight  line. 
One  way  of  locating  the  holes  is  by  means  of  steel  buttons 


located  in  a straight  line  by  being  brought  in  contact  with 
a straightedge  and  placed  at  the  correct  center-to-centei 
distance  by  contact  measurements.  Another  method  that 
will  produce  very  accurate  results  and  is  applicable  to  a 
great  many  different  jobs  is  shown  in  Fig.  18.  A number 
of  hardened  steel  disks,  as  a , a , equal  in  diameter  to  the 
center-to-center  distance  of  the  holes,  are  put  into  a frame 
and  held  in  contact  with  one  another  and  with  one  side 
of  the  frame  that  forms  a straightedge  by  means  of  the 


TOOLMAKING. 


35 


§ 27 


setscrews  b,  b.  Evidently,  if  the  disks  are  pierced  by  holes 
central  with  their  outside,  and  if  holes  are  drilled  and  reamed 
through  these  disks,  these  holes  will  be  equidistant  and  on  a 
straight  line. 

The  accuracy  in  spacing  attainable  depends  primarily  on 
the  accuracy  in  diameter  of  the  disks  and  the  concentricity 
of  the  holes  in  them,  while  the  accuracy  within  which  the 
holes  lie  in  a straight  line  depends  on  the  stiffness  and  on 
the  accuracy  with  which  the  straightedge  of  the  frame  is 
formed.  The  error  in  the  center-to-center  distance  of  the 
end  holes  is  evidently  the  product  of  the  error  in  diameter 
of  a single  disk  and  the  number  of  disks.  With  proper 
facilities,  there  should  be  little  trouble  in  making  the  di- 
ameter of  the  disks  equal  within  an  insensible  amount  of 
variation;  and  as  the  diameter  need  not  vary  more  than 
.0001  inch  from  the  true  diameter,  and  while  it  is  feasible 
to  make  the  holes  in  the  disks  concentric  with  the  outside 
within  a negligible  amount  of  variation,  it  follows  that  the 
total  error  between  the  end  holes  should  be  very  small  indeed. 

When  a rather  large  number  of  holes  are  required,  this 
device  may  be  made  to  include,  say,  six  holes  and  then  be 
shifted  forwards,  being  centered  by  a pin  passing  through 
the  first  disk  into  the  last  hole.  If  this  is  adopted,  the 
whole  device  must  be  shifted  along  a straightedge  of  suffi- 
cient length;  the  outside  of  the  frame  must  then  be  finished 
parallel  to  the  line  passing  through  the  centers  of  the  disks. 

34.  Another  method  of  mechanically  spacing  holes  in 
work  is  to  locate  the  first  hole  by  means  of  a center-punch 
mark  or  a steel  button,  the  work  being  mounted  on  the  face 
plate  of  a lathe.  A straightedge  is  then  clamped  to  the 
face  plate  in  contact  with  one  side  of  the  work.  After  the 
first  hole  is  finished,  a vernier  depth  gauge  or  a special 
micrometer  head  is  clamped  opposite  the  end  of  the  work 
and  the  distance  to  the  work  measured.  The  clamps  on  the 
work  are  then  loosened  and  the  piece  shifted  the  proper 
distance  along  the  straightedge,  the  distance  being  meas- 
ured by  the  vernier  or  micrometer.  The  work  is  again 


TOOLMAKING. 


36 


§27 


clamped  and  the  second  hole  finished.  Fig.  19  shows  a 
handy  form  of  special  micrometer  that  may  be  used  for 
such  work. 


Fig.  19. 


Holes  in  work  can  also  be  spaced  by  mounting  the  work 
on  the  table  of  a milling  machine  and  obtaining  the  spacing, 
either  vertical  or  horizontal,  by  means  of  the  graduated 
dials  on  the  feed-screws. 


DIVIDING  BY  CORRECTING  THE  ACCUMULATED  ERROR. 

35,  Fig.  20  shows  a modification  of  the  method  ex- 
plained in  connection  with  Fig.  17  for  dividing  a circle.  In 
this  case,  the  problem  is  to  subdivide  the  distance  between 
two  holes  into  an  equal  number  of  divisions.  The  movable 
arms  of  Fig.  17  are  here  replaced  by  a block  with  movable 
slides  a and  b,  which  carry  the  bushings.  In  its  simplest 
form,  the  device  is  without  any  adjusting  screws;  for  refined 


(l 


Fig.  20. 


work,  these  screws  are  needed,  and  they  may  be  applied 
either  to  one  or  to  both  slides,  as  desired.  By  tightening 
the  screws  c,  c,  the  slides  and  block  are  locked  together 
without  disturbing  the  center-to-center  distance  of  the 
bushings.  The  device  must  be  used  in  conjunction  with  a 
straightedge  if  the  holes  are  to  be  on  a straight  line,  or  a 
curved  guide  of  suitable  curvature  if  the  holes  lie  on  a circular 


27 


TOOLMAKING. 


37 


arc.  The  side  d is  intended  to  slide  along  the  straightedge 
or  the  curved  guide  and  must  be  made  to  suit. 

Suppose  that  the  distance  between  two  holes  is  to  be  sub- 
divided by  a number  bf  equally  spaced  holes  that  are 
required  to  lie  on  a straight  line.  A straightedge  of  suffi- 
cient length  is  clamped  to  the  work  in  such  a position  that 
when  the  device  is  in  contact  with  the  straightedge,  a 
closely  fitting  plug  will  pass  through  the  bushings  into  both 
holes  when  shifted  from  one  to  the  other.  The  slides  are 
then  set  about  the  required  distance  apart  and  locked.  A 
plug  is  pushed  through  one  bushing  into  the  hole  in  the 
work  and  a hole  is  drilled  and  reamed  through  the  other 
bushing.  The  device  is  then  shifted  along  and  the  other 
holes  are  put  through  the  work. 

When  the  last  hole  has  been  reamed,  the  distance  between 
it  and  the  end  hole  is  most  likely  to  differ  somewhat  from  the 
center-to-center  distance  between  the  bushings.  The  differ- 
ence is  then  split  in  accordance  with  the  direction  in  which 
observation  showed  the  center-to-center  distance  to  vary 
and  the  operation  of  reaming  is  repeated.  This  process  is 
repeated  until  plugs  passing  through  both  bushings  will 
enter  the  end  hole  and  the  one  adjoining  it.  When  making 
a device  as  shown  in  Fig.  20,  it  is  to  be  observed  that  it  is 
essential  to  have  the  centers  of  both  bushings  at  the  same 
distance  from  the  edge  d when  it  is  required  that  the  holes 
in  the  work  shall  be  in  a straight  line. 


I 


GAUGES  AND  GAUGE  MAKING. 


GAUGES. 


CLASSIFICATION  OF  GAUGES. 

1.  Most  of  the  measurements  made  in  the  machine  shop 
consist  of  determining  linear  distances,  or  of  the  measuring 
of  angles;  hence,  only  gauges  intended  for  such  work  will 
be  considered  in  this,  section.  A gauge  may  briefly  be 
defined  as  any  standard  of  comparison.  Gauges  may, 
according  to  their  purpose,  be  divided  into  two  general 
classes — reference  and  zvor king  gauges. 

2,  Reference  gauges  are  gauges  that  represent  either 
an  accurate  subdivision  of  the  ultimate  standard  of  refer- 
ence, or  some  arbitrary  size  or  shape  adopted  for  some  pur- 
pose and  required  to  be  preserved.  The  ultimate  standard 
of  reference  may  be  the  standard  bar  for  the  metric  system 
or  the  standard  bar  for  the  imperial  standard  yard.  Refer- 
ence gauges  are  commonly  kept  for  testing  other  gauges  and 
hence  are  often  called  master  gauges.  They  are  of  many 
shapes  and  forms,  which  depend  on  the  purpose  for  which 
they  are  intended.  Among  the  more  common  forms  may 
be  mentioned  the  standard  end-measuring  pieces  made  by 
the  Pratt  & Whitney  Company,  and  the  standard  disks  and 
end-measuring  pieces  made  by  the  Brown  & Sharpe  Manu- 
facturing Company.  Among  the  reference  gauges  of  a more 
special  class  may  be  mentioned  the  taper  gauges , which  show 
the  exact  taper  of  the  different  Morse  taper  shanks  for  twist 

§ 28 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


GAUGES  AND  GAUGE  MAKING. 


28 


drills;  the  master  gauges  for  these  are,  of  course,  in  the 
possession  of  the  Morse  Twist  Drill  Company.  In  a broad 
sense,  the  ultimate  standard  of  reference  in  the  United 
States,  which  consists  of  the  metric  bar  in  the  possession  of 
the  Government,  is  a reference  gauge,  as  are  also  bronze 
No.  11  and  Low  Moore  Iron  No.  57,  which  were  originally 
brought  to  this  country  to  represent  the  English  standard 
yard. 

3.  Working  Gauges. — There  are  two  general  classes 
of  working  gauges  used  in  the  shop — first,  those  that 
represent  an  integral  or  fractional  subdivision  of  the  ulti- 
mate standard  of  reference,  whether  it  be  the  imperial  yard  or 
standard  meter  bar;  second,  those  that  are  intended  for  pre- 
serving some  special  form  and  are  used  for  duplicating  work. 
To  the  second  class  belong  all  taper  gauges  and  an  infinite 
variety  of  special  gauges  for  various  irregular  parts,  such  as 
occur  in  the  manufacture  of  guns,  sewing  machines,  and 
other  similar  articles. 

4.  Definite  and  Limit  Gauges. — Gauges  may  also 
be  subdivided  into  definite  gauges  and  limit  gauges.  Defi- 
nite gauges  are  those  that  establish  a certain  linear  or 
angular  dimension,  but  do  not  indicate  any  variations  from 
the  standard  of  the  gauge.  A limit  gauge  really  con- 
sists of  two  definite  gauges  that  represent  the  limits  within 
which  the  piece  in  question  will  pass  inspection.  Evidently 
a piece  of  work  to  pass  inspection  of  the  limit  gauge  must 
be  of  such  size  that  it  is  smaller  than  the  large  gauge  and 
larger  than  the  small  gauge  of  the  pair. 


ACCURACY  ATTAINABLE  IN  GAUGE  WORK. 

5.  Limits  of  Accuracy. — The  definite  gauges  in  most 
common  use  are  plug  and  ring  gauges,  snap  gauges, 
end-measure  rods,  and  taper  gauges.  Of  these  gauges, 
the  first  three  named  establish  definite  linear  dimensions, 
and  the  last  named  establishes  an  angular  dimension. 


§28 


GAUGES  AND  GAUGE  MAKING. 


3 


Definite  gauges  in  general,  and  also  some  limit  gauges, 
cannot  usually  be  made  without  suitable  measuring  instru- 
ments. The  kind  of  measuring  instrument  to  be  employed 
naturally  depends  on  the  accuracy  with  which  a size  is  to  be 
established.  In  general,  the  limits  of  accuracy  that  may  be 
obtained  by  the  aid  of  the  various  measuring  instruments 
are  as  follows: 

1.  Using  a graduated  standard  scale,  made  by  a reputable 
maker,  that  has  its  graduations  cut  in  a dividing  machine  and 
setting  calipers  to  it,  the  limit  may  be  placed  at  .002  inch; 
that  is,  the  size  established  may  be  .002  inch  above  or  below 
the  true  size,  giving  a total  variation  of  .004  inch. 

2.  Using  a vernier  caliper,  if  made  by  a reputable  maker, 
the  total  variation  need  not  exceed  .001  inch.  Remember 
that  the  total  variation  is  twice  the  limit  of  accuracy. 

3.  By  the  aid  of  a good  micrometer  kept  in  first-class 
order  and  tested  frequently  by  standard  end-measure  pieces 
or  reference  disks,  gauges  can  be  made  in  which  the  total 
variation  is  within  .0001  inch. 

4.  When  the  total  variation  is  to  be  less  than  .0001  inch, 
a micrometer  is  not  reliable  enough,  and  recourse  must 
be  had  to  a standard  bench-measuring  machine  in  which 
a contact  piece  takes  the  place  of  the  sense  of  touch  of 
the  toolmaker.  With  such  a machine,  work  can  be  meas- 
ured within  a limit  of  accuracy  of  .00002  inch,  or  a total 
variation  of  .00004  inch.  This  may  be  considered  ordinarily 
as  the  commercial  limit  of  accuracy ; it  is  rarely  required 
for  gauges  other  than  reference  gauges. 

5.  Measurements  closer  than  those  possible  with  a bench- 
measuring machine  are  made  by  means  of  a comparator. 
Work  of  this  class  is  outside  of  the  legitimate  domain  of  the 
toolmaker  and  comes  within  the  realm  of  the  scientist,  since 
it  cannot  be  justly  classified  under  the  heading  of  commer- 
cial work. 

6.  Needless  Accuracy  in  Gauges. — In  gauge  work, 
the  toolmaker  must  guard  against  needless  accuracy,  since 
the  cost  of  gauges  is  increased  at  an  enormous  rate  with 


4 


GAUGES  AND  GAUGE  MAKING. 


§28 


every  reduction  in  the  limit  of  variation.  The  purpose  that 
the  gauge  is  intended  for  will  usually  indicate  the  permissible 
limit  of  variation,  and  thus,  by  the  exercise  of  judgment, 
allow  a proper  method  of  making  it  to  be  chosen.  This  in 
turn  will  allow  gauges  to  be  produced  that  are  not  only 
“good  enough”  but  also  reasonable  in  first  cost.  For 
instance,  a gauge  intended  for  testing  the  accuracy  of  a 
micrometer  naturally  needs  to  be  accurate  in  itself,  within 
the  commercial  limit  of  accuracy;  while  a gauge  intended 
for  trying  the  bore  of  a large  steam-engine  cylinder,  say, 
40  inches  in  diameter,  would  usually  be  accurate  enough  for 
the  purpose  if  it  varies  not  more  than  .01  inch  from  its  true 
dimension.  Likewise,  a gauge  intended  for  the  blacksmith, 
who,  on  medium-sized  work,  would  consider  it  very  good 
indeed  if  he  works  to  within  T^-  inch  variation,  would  be  need- 
lessly accurate  if  made  closer  than  inch  to  its  true  size. 

Sometimes  it  is  rather  difficult  to  decide  on  how  close  a 
gauge  must  agree  with  its  nominal  size;  in  that  case,  the 
toolmaker  must  use  his  judgment.  For  instance,  suppose 
that  some  part  of  a job  is  to  be  turned  cylindrical  and  to  fit 
a hole  in  some  other  piece,  the  two  pieces  of  work  being  done 
by  different  men  working  to  gauges.  Then,  while  it  is  of 
paramount  importance  that  the  gauges  used  by  the  two  men 
agree  with  each  other,  this  does  not  necessarily  imply  that 
the  actual  size  of  the  gauges  must  agree  with  their  nominal 
size  within  the  utmost  degree  of  refinement.  Judgment 
alone  can  determine  the  comparative  accuracy  required. 


MATERIALS  USED  FOR  GAUGES. 

7.  Hardened-Steel  Gauges. — The  material  most  com- 
monly used  for  gauges  is  tool  steel,  although  for  some  work 
machinery  steel  is  “ good  enough.”  The  treatment  of  tool 
steel  for  gauge  work  depends  somewhat  on  the  accuracy 
required  and  the  hardness  of  the  gauge.  When  a gauge 
made  of  tool  steel,  hardened  all  over,  and  probably  clear 
through,  or  nearly  so,  is  finished  to  an  accurate  size  imme- 
diately after  hardening,  it  has  been  observed  that,  frequently, 


GAUGES  AND  GAUGE  MAKING. 


5 


§28 

there  is  a gradual  change  of  size  or  shape  taking  place, 
which,  in  the  course  of  time,  may  cause  a sensible  deviation. 
This  change  of  shape  is  ascribed  to  a rearrangement  of  the 
molecules  of  the  steel,  whose  former  arrangement  has  been 
violently  disturbed  by  the  hardening  process.  Fortunately, 
this  change  of  shape,  which,  according  to  observation,  lasts 
for  about  a year,  is  not  very  large,  rarely  exceeding  .0005  inch 
per  inch  diameter,  hence  it  need  not  be  taken  into  account 
for  any  but  very  accurate  gauges.  For  reference  gauges 
made  within  a limit  of  variation  of  .00002  inch,  it  must  be 
taken  into  account  if  the  nominal  size  or  shape  of  the  gauge 
is  to  be  preserved.  The  usual  way  is  to  rough  out  the 
gauge  directly  after  hardening  to  within  a small  amount, 
say,  .002  inch  per  inch  diameter  for  a plug  gauge,  and  then 
allow  it  to  “ season,”  or  “age,”  as  it  is  called,  for  about  a 
year  before  finishing  it  to  size. 

Personal  observation  has  led  us  to  believe  that  this  season- 
ing process  can  be  greatly  hastened  by  drawing  the  hardened 
gauge  to  a straw  color  after  it  has  been  roughed  out. 
Undoubtedly,  a change  takes  place  even  after  this,  but  we 
believe  the  amount  is  so  small  as  to  be  insensible,  and  hence 
negligible  for  commercial  work.  As  a matter  of  course,  this 
method  of  seasoning  steel  leaves  the  gauge  softer,  and  hence 
it  will  wear  faster.  Whether  this  is  a matter  of  sufficient 
moment  to  prohibit  the  use  of  this  method,  everybody  must 
decide  for  himself. 

8.  Soft  Steel  Gauges. — Reference  gauges  that  are 
rarely  used  are  often  left  soft;  they  are  then  made  from 
well-annealed  tool  steel,  which  does  not  seem  to  change  a 
sensible  amount  with  age.  Machinery  steel,  if  well  annealed 
in  case  any  forging  has  been  done  in  making  the  gauge,  will 
keep  its  shape  and  size  very  well;  being  much  softer  than 
tool  steel,  it  will  naturally  wear  much  faster.  Gauges  that 
are  made  from  tool  steel,  but  hardened  only  in  parts,  do  not 
seem  to  be  affected  much,  if  any,  by  the  “aging,”  provided, 
of  course,  that  the  hardening  extends  over  but  a very  small 
part  of  the  gauge. 


C.  5.  III.— 36 


6 


GAUGES  AND  GAUGE  MAKING. 


§28 

GAUGE  MAKING. 


PLUG  AND  RING  GAUGES. 

9.  Making  » Plug  Gauge. — To  make  a plug  gauge, 

turn  down  a piece  of  well-annealed  tool  steel,  on  centers  of 
liberal  size,  making  a grinding  allowance  of  .01  inch  up  to 
\ inch  diameter,  .02  inch  up  to  f inch  diameter,  and  .03  inch 
up  to  1J  inches  diameter.  Above  that  size,  .04  inch  should 
prove  ample.  Flute  or  nurl  the  shank,  then  turn  a groove, 
as  a , Fig.  1,  with  a half-round  tool,  at  a distance  from  the 


end  sufficient  to  come  clear  of  the  countersink.  Turn  the 
groove  deep  enough  to  leave  the  diameter  of  the  neck  about 
33¥  inch  for  a J-inch  plug  gauge,  and  inch  for  sizes  up  to 
\ inch.  For  sizes  up  to  f inch,  it  may  be  ^ inch  in  diam- 
eter, and  \ inch  for  sizes  up  to  1|-  inch.  For  sizes  above 
this,  leave  the  neck  about  | inch  in  diameter.  The  dis- 
tance b may  be  about  one-tenth  the  diameter  of  the  gauge, 
plus  .2  inch.  Harden  all  over  and  then  grind  in  a grinding 
machine  to  within  a small  amount  of  the  finished  size.  Now, 
let  the  steel  season  by  age,  or  temper  it  to  hasten  the  sea- 
soning. Then  grind  to  within  .001  inch  of  the  finished  size, 
and  as  truly  cylindrical  as  possible.  Finish  by  lapping  with 
the  finest  flour  emery,  using  a speed  lathe  for  the  sake  of 
convenience,  and  a suitable  lap. 

The  process  of  lapping  naturally  heats  the  gauge  consid- 
erably; if  it  is  measured  while  hot,  it  will  be  below  size  when 
it  has  cooled  to  the  normal  temperature,  owing  to  the  con- 
traction of  the  steel  in  cooling.  For  this  reason,  the  gauge 
must  be  cooled  to  the  temperature  of  the  room  before  it  is 


28 


GAUGES  AND  GAUGE  MAKING. 


7 


measured,  if  any  degree  of  accuracy  is  required.  To  cool 
it,  insert  it  in  a bucket  of  water  that  has  been  in  the  room 
for  an  hour  or  more,  leaving  it  in  the  bucket  long  enough 
to  cool  down  to  the  temperature  of  the  water.  Repeat  the 
lapping  until  the  gauge  is  the  correct  size,  within  the  limit 
of  accuracy  determined  necessary.  All  measuring  must  be 
done  on  the  cylindrical  part  of  the  gauge  itself,  but  never 
on  the  disk  at  the  end.  In  sliding  the  lap  back  and  forth 
while  lapping,  the  lap  is  sure  to  cut  faster  at  the  extreme 
end  of  the  gauge,  which  is  therefore  ground  slightly  taper- 
ing, as  careful  measuring  will  show.  In  order  that  the  gauge 
may  be  straight  throughout,  the  disk  is  formed  at  the  end 
and  then  broken  off  after  the  gauge  is  lapped  to  size.  To 
finish  the  end  nicely,  grind  it  off  square  in  a grinding 
machine,  holding  the  gauge  in  a chuck. 

lO.  Lap  for  Finishing  Plug  Gauges. — The  lap 

may  be  made  in  various  ways.  A very  satisfactory  con- 
struction is  shown  in  Fig.  2.  The  lap  proper  consists  of  a 


Fig.  2. 


ring  bored  parallel  inside  and  to  a diameter  about  .001  inch 
larger  than  the  outside  diameter  of  the  gauge.  The  outside 
of  the  ring  is  turned  tapering  on  a taper  of  -J-  inch  per  foot; 
it  is  fitted  to  a collar  somewhat  shorter  than  the  lap.  The 
lap  is  split  by  three  cuts,  two  of  which  terminate  at  a short 
distance  from  the  exterior  surface.  The  third  cut  is  carried 
clear  through.  Evidently,  driving  the  lap  into  its  collar 
closes  the  lap  in.  The  most  satisfactory  material  for  it  is 


8 


GAUGES  AND  GAUGE  MAKING. 


28 


close-grained  cast  iron.  In  the  lap  shown,  the  friction 
between  the  collar  and  the  lap  is  usually  sufficient  to  pre- 
vent the  lap  from  turning  in  its  collar.  If  desired,  a small 
pin,  as  <?,  may  be  inserted.  The  length  of  the  lap  should 
not  be  less  than  three  times  the  diameter  of  the  gauge. 
With  the  construction  shown,  the  lap  is  closed  in  practically 
uniform  throughout  its  length ; this  is  necessary  in  order  to 
produce  good  work. 

11.  Making  Large  Plug  Gauges. — Large  plug 
gauges  may  be  made  in  two  parts.  The  body  may  then  be 
made  of  machinery  steel,  and  a hardened  tool-steel  bushing 
that  has  been  ground  on  the  inside  after  hardening  may  be 
forced  over  the  body  and  then  ground  and  lapped  to  size. 
The  bushing  being  rather  thin,  the  change  in  shape  or  size 
while  seasoning  is  infinitesimal.  The  inside  of  the  bushing 
may  be  ground  out  slightly  tapering,  say.  on  a taper  of 
T3g  inch  per  foot;  the  body  should  then  be  ground  to 'fit  very 
nicely.  Owing  to  the  bushing  being  hard,  great  care  must 
be  exercised  not  to  drive  it  on  too  much,  since  it  is  easily 
split.  Have  both  body  and  bushing  perfectly  clean  and  free 
from  oil  before  driving  the  bushing  home.  Very  little  dri- 
ving will  then  hold  the  bushing  so  tight  that  it  cannot  be 
loosened  by  any  reasonable  usage. 

12.  Classes  of  Ping  Gauges. — Ring  gauges  may 

be  made  in  two  ways:  They  may  be  made  of  a solid  block  of 
tool  steel  hardened  all  over,  or  they  may  have  a body  of 
machinery  steel  into  which  a hardened  tool-steel  bushing 
has  been  forced.  Each  of  these  methods  has  its  own  advan- 
tages and  disadvantages.  As  far  as  the  solid-ring  gauge  is 
concerned,  it  is  cheaper  in  first  cost,  and  not  liable  to  be 
indented  by  accidental  blows;  on  the  other  hand,  it  is  liable 
to  crack  in  hardening,  will  change  in  shape  or  size  while 
seasoning,  and  is  worthless  when  worn.  The  second  method 
of  construction  mentioned  is  slightly  more  expensive;  this, 
however,  is  offset  by  the  comparative  absence  of  change  in 
seasoning  and  the  fact  that  when  slightly  worn  it  can  be 
restored  to  its  former  size  by  driving  the  bushing  home, 


28 


GAUGES  AND  GAUGE  MAKING. 


9 


which  is  made  slightly  tapering  on  the  outside  for  this  pur- 
pose. Furthermore,  when  worn  so  as  to  be  unserviceable,  a 
new  bushing  can  be  made  at  less  cost  than  a new  solid-ring 
gauge  can  be  made.  Knowing  the  advantages  and  disad- 
vantages of  each  method,  the  toolmaker  must  decide  for 
himself  which  one  to  adopt. 

1 3.  Making  a Solid  Ring  Gauge. — To  make  a solid 
gauge,  use  a piece  of  annealed  tool  steel  long  enough  to  give 
the  form  shown  in  Fig.  3 (a).  Make  the  height  a of  the 


(a)  (b) 

Fig.  3. 


projection  about  one-tenth  the  gauge  diameter  plus  .2  inch. 
Make  the  diameter  of  these  projections  from  -J-  to  T3^-  inch 
larger  than  the  gauge  diameter,  and  leave  an  ample  grind- 
ing allowance  o'n  the  inside.  Finish  the  outside,  stamp  the 
size  on  the  ring,  and  then  harden.  For  the  larger  .sizes, 
now  grind  the  inside  to  within  a small  fraction  of  the  fin- 
ished diameter  if  an  internal  grinding  device  is  available;  if 
not,  grind  out  by  lapping  in  the  same  manner  as  must  be 
done  for  sizes  too  small  to  admit  of  grinding.  Then  season 
and  finally  bring  to  the  finished  size  by  lapping,  using  the 
plug  previously  made  as  a gauge.  Great  care  must  be  taken 
to  have  plug  and  gauge  at  the  same  temperature  while  try- 
ing the  fit ; also,  both  the  plug  and  ring  must  be  absolutely 
free  from  the  abrading  material  used  for  lapping.  The 
operation  of  lapping  will  leave  the  ends  of  the  gauge  slightly 
bell-mouthed;  when  the  plug  just  commences  to  enter  at 
either  end,  it  will  show  the  toolmaker  that  the  ring  gauge 


10 


GAUGES  .AND  GAUGE  MAKING. 


28 


is  lapped  very  nearly  to  the  finished  size.  For  the  final  lap- 
ping, the  very  finest  of  flour  emery  must  be  used  with  a 
copious  supply  of  oil. 

The  fit  of  the  plug  in  the  ring  should  simply  be  perfect. 
It  should  be  so  perfect  that  when  the  temperature  of  the 
plug  is  raised  to  blood  heat  by  holding  it  in  the  hand  for  a 
few  minutes,  it  will  not  enter  the  ring  gauge,  which  is  here 
supposed  to  be  at  a temperature  of  about  70°.  In  trying 
the  fit,  try  to  enter  the  plug  by  a combined  sliding  and 
rotary  motion;  should  the  plug  stick,  do  not  drive  it  out 
under  any  circumstances,  but  heat  the  ring  gauge  a little, 
which  will  quickly  expand  it  enough  to  allow  the  plug  to  be 
withdrawn  by  hand.  If  the  plug  be  driven  out  when  stuck, 
there  is  a liability  of  badly  scoring  both  the  plug  and  the 
ring  gauge.  When  the  ring  gauge  has  been  lapped  to  a 
perfect  fit,  the  projections  at  each  end  are  ground  off  flush 
with  the  faces.  The  hole  will  then  be  perfectly  straight. 

14.  Making  an  Inserted-Busliing  Ring  Gauge. 

When  making  a ring  gauge  with  an  inserted  bushing,  the 
machinery-steel  collar  may  be  made  first,  finishing  it  all 
over.  The  central  hole  is-  to  be  bored  and,  preferably, 
ground  afterwards  slightly  tapering,  say,  about  T\  inch  per 
foot,  making  it  about  one-tenth  the  diameter  plus  .1  inch 
larger  than  the  size  of  the  ring  gauge.  Turn  and  bore  the 
tool-steel  bushing,  leaving  a grinding  allowance  on  the 
inside  and  outside.  Make  the  bushing  long  enough  so  that 
when  driven  home  it  will  project  at  least  one-tenth  the  gauge 
diameter  plus  .2  inch  on  each  side.  Harden  the  bushing  and 
then  grind  or  lap  the  inside  true  and  round  to  within,  say, 
.001  inch  of  the  finished  size.  Place  the  bushing  on  a true 
running  arbor  and  grind  the  outside  to  fit  the  tapering  hole 
in  the  collar.  Remove  from  the  arbor  and  drive  the  bushing 
home  in  the  collar,  driving  lightly.  Finish  the  gauge  to 
size  by  lapping  it  to  fit  the  plug.  Grind  off  the  projecting 
ends  of  the  bushing  and  finish  by  polishing,  if  a fine  external 
finish  is  desired.  A slight  amount  of  wear  can  be  taken  up 
by  driving  the  bushing  farther  into  its  hole. 


§28 


GAUGES  AND  GAUGE  MAKING. 


11 


1 5.  Laps  for  Ring  Gauges. — There  are  various  ways 
in  which  the  lap  for  lapping  the  hole  true  and  straight  may 
be  made.  Many  toolmakers  believe  that  the  form  shown  in 
Fig.  4 makes  the  most  satisfactory  lap  for  this  work.  It 
consists  of  a mandrel  turned  tapering  about  inch  per  foot 
and  a split  shell  bored  to  fit  the  mandrel.  Cast  iron  will 
make  a very  satisfactory  material  for  the  shell,  which  is 
turned  about  .001  inch  below  the  size  of  the  hole  in  the 
gauge.  It  is  most  conveniently  turned  on  its  own  arbor, 
being  split  after  turning.  It  is  advisable  to  cut  two  shallow 


Fig.  4. 


slots,  as  a,  a , into  the  shell;  these,  in  conjunction  with  the 
slot  that  splits  the  shell,  will  act  as  reservoirs  for  the  abra- 
ding material  and  oil.  The  depth  of  these  two  slots  should 
be  greatest  for  a thick  shell;  they  will  then  facilitate  the 
expanding  of  the  lap,  which  is  done  by  driving  it  farther  on 
the  mandrel.  If  the  lap  has  been  used  for  roughing  out  the 
hole,  and  has  in  consequence  been  expanded  considerably, 
it  will  be  somewhat  out  of  round.  Hence,  it  is  recom- 
mended that  before  the  hole  is  lapped  to  final  size,  the  lap 
should  be  ground  true  and  round  in  a grinding  machine. 
The  lap  simply  must  be  round  in  order  to  lap  the  hole  true. 
The  length  of  the  shell  should  not  be  less  than  twice  the 
height  of  the  ring  gauge;  it  can  advantageously  be  made 
three  times  the  height. 


1 6.  Proportions  of  Plug  and  Ring  Gauges. — There 
is  no  recognized  standard  of  proportions  for  plug  gauges 
and  ring  gauges.  To  aid  the  toolmaker  in  selecting  dimen- 
sions, the  proportions  given  by  the  following  formulas  may 
be  used.  In  these  formulas,  d is  the  diameter  of  the  plug 
gauge. 


12 


GAUGES  AND  GAUGE  MAKING. 


28 


Length  of  cylindrical  part  of  plug  — 1.8  d A inch. 


These  formulas  should  not  be  used  for  plug  and  ring 
gauges  exceeding  3 inches  in  gauge  diameter. 

Example. — A 1-inch  plug  and  ring  gauge  is  to  be  made.  About 
what  proportions  may  be  adopted  ? 

Solution. — Applying  the  formulas  given,  we. get:  Length  of  cylin- 
drical part  = 1.8  d + .4  in.  =1.8x1  + -4  in.  = 2.2  in. ; length  of  handle 
= .5 d +-  1.5- in.  = .5  X 1 4-  1.5  in.  = 2 in. ; diameter  of  handle  = .5  d 
+ .2  in.  = .5  X 1 +-  -2  = .7  in. ; height  of  ring  gauge  = .9  d +-  .3  in. 
= .9  X 1 + .3  in.  = 1.2  in. ; diameter  of  ring  gauge  = 2.2  d + .5  in. 
= 2.2  X 1 +-  -5  in.  = 2.7  in.  Ans. 

In  a plug  gauge  and  a ring  gauge,  the  only  essential  sizes 
are  the  gauge  sizes;  all  other  dimensions  are  approximate 
and  close  enough  if  made  within  inch  of  the  dimensions 
adopted.  It  is  a waste  of  time  and  an  evidence  of  misdi- 
rected skill  to  take  much  pains  to  work  closer  as  far  as  these 
dimensions  are  concerned. 

17.  Limit  of  Variation  for  Limit  Gauges. — Plug 

and  ring  gauges  establish  a definite  size;  by  trying  them 
into  a hole  or  over  the  shaft,  they  show  if  the  hole  or  shaft 
is  the  correct  size.  They  do  not  show,  however,  the  amount 
of  variation  from  the  true  size,  nor  whether  the  variation  in 
the  size  of  the  hole  or  the  shaft  is  sufficient  to  prevent  one 
from  fitting  the  other  with  the  requisite  degree  of  accuracy, 
or  whether  they  will  go  together  at  all.  There  is  very  little 
work  indeed  that  requires  to  be  as  close  a fit  as  a plug  gauge 
into  its  ring  gauge;  in  nearly  all  work,  quite  an  appreciable 
deviation  from  this  degree  of  fit  is  permissible.  Naturally, 
the  amount  of  deviation  varies  with  the  circumstances  of 
each  particular  case.  Furthermore,  to  finish  a shaft,  and 
bore  a hole  to  receive  it,  to  an  accurate  size  is  a very  expen- 
sive job,  and  rarely  necessary.  Then,  in  order  to  prevent 
needless  accuracy  in  finishing  two  pieces  of  cylindrical  work 


Length  of  handle 
Diameter  of  handle 
Height  of  ring  gauge 
Diameter  of  ring  gauge 


= .5  d -(-  1.5  inches, 
= .5  d .2  inch. 

= . 9 d 4-  .3  inch. 

= 2.2  d-\-  .5  inch. 


§28 


GAUGES  AND  GAUGE  MAKING. 


IB 


that  are  to  fit  each  other,  limit  gauges  are  employed. 
Thus,  if  a shaft  is  to  be  1 inch  in  diameter,  and  it  has  been 
decided  from  previous  experience  and  observation  that  the 
fit  will  be  close  enough  if  there  is. 002-inch  variation  between 
the  size  of  the  shaft  and  the  size  of  the  hole,  two  sets  of 
plug  and  ring  gauges  differing  from  each  other  by  the  allow- 
able variation  may  be  used  as  limit  gauges.  One  of  the 
sets  would  usually  be  made  one-half  the  allowable  variation 
larger  than  the  nominal  size,  and  the  second  set  would  be 
made  just  as  much  smaller.  In  using  the  plugs,  the  smaller 
plug  must  enter  the  hole  and  the  larger  plug  must  not  enter. 
Likewise,  the  larger  ring  gauge  must  go  over  the  shaft  and 
the  smaller  one  must  not  go  over.  If  this  is  the  case  with 
both  shaft  and  hole,  it  is  evident  that  the  total  variation  in 
the  fit  is  not  more  than  .002  inch  for  the  case  considered, 
and  may  be  considerably  less. 

Now,  suppose  that  it  has  been  decided  that  the  shaft  must 
fit  the  hole  with  a given  minimum  amount  of  clearance.  In 
that  case,  the  two  internal  limit  gauges  must  be  smaller 
than  their  corresponding  internal  gauges  by  an  amount 
equal  to  the  given  minimum  amount  of  clearance.  Thus,  if 
the  clearance  is  to  be  at  least  .001  inch,  and  the  shaft  and 
hole  may  vary  .001  inch  from  the  true  dimension,  which  is, 
say,  1 inch,  then  the  internal  limit  gauge  may  be  made 
.9995  and  .9985  inch,  and  the  external  limit  gauge  1.0005  and 
1.0015  inches. 

18.  Distinguishing  Marks  for  Limit  Gauges. 

There  are  no  special  directions  required  for  making  cylin- 
drical limit  gauges.  It  is  well,  however,  to  stamp  the  size 
on  all  the  gauges  and  the  words  “go  in  ” on  the  smaller  plug 
gauge  and  larger  ring  gauge;  on  the  larger  plug  gauge  and 
smaller  ring  gauge,  the  words  “not  go  in  ” may  be  stamped. 
Another  plan  of  distinguishing  between  the  larger  and  the 
smaller  gauges  that  will  save  the  operator  the  time  required 
to  read  the  size  and  words,  is  to  make  the  handles  of  the 
plug  gauges  and  the  outside  of  the  ring  gauges  of  different 
form.  Thus,  the  handle  of  the  larger  plug  gauge  and  the 


14 


GAUGES  AND  GAUGE  MAKING. 


§ 28 

outside  of  the  smaller  ring  gauge  may  be  fluted  with  semi- 
circular flutes,  while  the  handle  of  the  smaller  plug  gauge 
and  the  outside  of  the  larger  ring  gauge  may  be  nurled 
with  a coarse  nurling  tool.  If  this  is  done,  the  operator 
that  uses  the  limit  gauges  will  quickly  discover  that  nurling 
stands  for  “not  go  in  ” and  fluting  for  “go  in.”  While  this 
may  appear  like  a small  matter  on  first  thought,  it  should 
be  remembered  that  careful  attention  to  such  small  details 
will  sensibly  increase  the  output  of  a machine  operator. 

A handy  method  of  constructing  a cylindrical-plug  limit 
gauge  is  shown  in  Fig.  5 ( a ).  Here  the  plug  gauge  is  made 


(a) 


(b) 

Fig.  5. 


of  two  different  diameters  separated  by  a neck  of  ample 
size.  The  difference  in  the  two  diameters  is  equal  to  the 
allowable  limit  of  variation.  Evidently,  if  this  gauge  is 
used,,  the  operator  can  gauge  a hole  faster  than  when  two 
separate  gauges  are  employed.  Judgment  will  indicate  when 
and  where  this  style  of  plug  gauge  can  be  used.  A some- 
what different  plug  limit  gauge  is  shown  in  Fig.  5 (b). 
Here  the  gauges  are  at  the  ends,  and  the  handle  is  between 
them.  The  larger,  or  “not  go  in,”  gauge  is  made  longer 
than  the  smaller  gauge,  so  that  one  look  will  be  sufficient  to 
inform  the  operator  which  end  is  the  larger.  As  it  seems 
natural  to  assume  that  the  longer  end  is  the  larger  in  diam- 
eter, it  is  recommended  that  it  be  made  thus. 


GAUGES  AND  GAUGE  MAKING. 


15 


§28 


SNAP  GAUGES. 

10.  Advantages  of  Snap  Gauges.  — A snap 
gauge  has  its  own  sphere  of  usefulness,  being  superior  for 
some  work  to  a ring  gauge.  In  the  first  place,  a snap  gauge 
is  adapted  to  measuring  work  having  a cross-section  other 
than  round ; for  cylindrical  work  done  between  centers,  it  is 
not  necessary  to  take  the  work  out  of  the  lathe  to  test  it;  it 
is  also  claimed  that  a deviation  from,  the  true  size  can  be 
more  readily  detected  by  it  than  by  a ring  gauge.  Further- 
more, by  applying  it  in  several  directions,  the  roundness  of 
work  can  be  tested.  This  cannot  be  done  with  a ring  gauge. 
It  is  easy  to  conceive  that  an  alleged  cylindrical  piece  of 
work  may  apparently  be  a very  good  fit  in  a ring  gauge,  and 
be  slightly  oval  at  the  same  time.  Unless  the  divergence 
from  a circle  is  rather  great,  the  ring  gauge  will  not  show 
it;  the  snap  gauge  will  show  a very  minute  deviation,  how- 
ever. It  can  also  be  used  for  measuring  a neck  between 
two  collars. 

20.  Form  of  Snap  Gauges. — Snap  gauges  may  be 
designed  in  a great  variety  of  forms,  to  suit  different  pur- 
poses and  conditions.  The  most 
common  form  of  an  external 
gauge  is  that  shown  in  Fig.  6. 

In  order  to  pass  over  cylindrical 
work,  the  depth  of  the  opening 
must  be  slightly  more  than  the 
radius  of  the  piece  ; that  is, 
slightly  over  half  the  gauge  size. 

When  a snap  gauge  of  this  kind 
is  intended  for  flat  work,  the  depth  of  the  opening  is  to  be 
made  to  suit  the  work.  In  order  that  the  size  of  the  gauge 
may  be  retained,  an  inside  end  gauge  may  be  made;  if  the 
size  of  the  snap  gauge  must  be  very  accurate,  an  inside 
gauge  is  absolutely  required  in  order  to  produce  the  correct 
size  of  opening.  When  snap  gauges  take  the  place  of  plug 
and  ring  gauges,  the  plug  gauge  is  replaced  by  the  inside 


16 


GAUGES  AND  GAUGE  MAKING. 


§ 28 


snap  gauge  shown  in  Fig.  7.  This,  in  its  simplest  form,  is  a 
flat  piece  of  tool  steel  with  a handle  formed  on  one  end  and 
circular  measuring  surfaces  of  the  correct  diameter  at  the 


other  end.  When  the  inside  snap  gauge  is  intended  solely 
for  holes  or  slots  of  rectangular  cross-section,  the  measur- 
ing surfaces  are  usually  made  to  form  parallel  plane  surfaces 
that  are  the  correct  distance  apart. 

21.  Snap  Limit  Gauges. — For  many  classes  of  work, 
the  snap  gauge  may  advantageously  be  used  as  a limit 
gauge.  It  may  then  be  formed  with  an  opening  at  each  end, 


as  shown  in  Fig.  8.  It  is  a good  idea  to  make  the  ends  of 
the  gauge  of  different  shape,  in  order  to  make  a distinction 
between  the  large  and  small  opening  ; thus,  the  gauge  may 


GAUGES  AND  GAUGE  MAKING. 


17 


§ 28 

taper  on  the  outside,  being  larger  at  the  end  that  has  the 
larger  opening.  A limit  snap  gauge  may  often  be  made 
advantageously  of  the  form  shown  in  Fig.  9.  If  thus  made, 
the  work  can  be  gauged  without  reversing  the  gauge,  thus 
effecting  a saving  of  time  and  muscular  effort  on  the  part 
of  the  operator. 

The  degree  of  accuracy  with  which  a snap  gauge  must 
represent  its  nominal  size  naturally  determines  the  method 
by  which  it  is  to  be  made.  Thus,  if  the  gauge  is  accurate 
enough  if  within  .01  inch  of  its  nominal  size,  and  if  slight 
wear  is  unobjectionable,  it  would  be  a decided  waste  of  time 
to  finish  the  gauge  dead  true  to  size  by  grinding  and  lapping 
If  the  limit  of  variation  is  not  to  exceed  .001  inch,  grinding 
will  usually  have  to  be  resorted  to,  and  if  the  wear  is  to 
be  kept  down  to  a minimum,  lapping  becomes  essential 
after  grinding. 

22.  Making  Snap  Gauges. — Except  when  the  size 
of  the  outside  gauge  is  so  large  that  an  inside  micrometer 
can  be  applied,  the  inside 
gauge  has  to  be  made 
first ; the  outside  snap 
gauge  is  then  finished  to 
fit  the  inside  gauge.  If  the  inside  gauge  simply  serves  -the 
purpose  of  a reference  gauge  to  preserve  the  gauge  size,  it 
may  conveniently  be  a cylindrical  bar  having  its  end  squared 
nicely  and  finished  to  the  correct  size.  A good  way  of 
making  such  a bar  is  shown  in  Fig.  10.  A piece  of  tool  steel 
about  £ inch  longer  than  the  inside  gauge  is  to  be,  is  turned 
between  centers,  and  then  necked  down  on  both  ends,  as 
shown.  The  two  disks  thus  formed  are  intended  to  be 
broken  off  finally,  in  order  to  get  rid  of  the  centers.  After 
turning,  harden  at  the  ends  or  all  over,  according  to  size. 
Grind  the  outside  straight  and  true  and  then  break  off  the 
disks.  After  this  is  done,  the  ends  are  ground  square  and 
flat  in  a grinding  machine,  holding  the  gauge  in  a chuck 
and  finishing  to  within  a small  amount  of  the  finished  size. 
The  final  bringing  to  size  is  to  be  done  by  lapping. 


18 


GAUGES  AND  GAUGE  MAKING. 


28 


In  order  to  insure  parallelism  of  the  two  measuring  sur- 
faces, it  is  recommended  that  the  device  shown  in  Fig.  11  be 

used  for  lapping.  This  little 
device  may  be  made  of  any 
suitable  piece  of  scrap.  As 
shown,  it  has  a central  hole 
bored  to  a good  sliding  fit  for 
the  gauge.  A narrow  ring  of 
liberal  outside  diameter  is 
faced  off  square  with  the  hole; 
this  may  be  done  at  the  same 
chucking  in  which  the  hole  is 
bored,  or  by  mounting  the  de- 
vice on  a true-running  arbor 
after  boring  the  hole  and  then 
facing  it  while  running  the 
centers.  The  inside  gauge  is  inserted 
into  the  hole  and  pushed  down  level  with  the  faced  end;  by 
moving  the  device  to  and  fro  on  a small,  planed,  cast-iron 
plate  charged  with  fine  emery  and  oil,  the  ends  of  the  gauge 
may  be  lapped  true  and  square,  and  parallel  to  each  other. 

Frequently,  it  is  most  convenient  to  make  the  inside 
gauge  from  drill  rod,  which  is  true  and  straight  enough  not 
to  require  any  finishing  on  the  outside.  If  the  gauge  is 
hardened  at  the  ends  only,  there  will  be  little  danger  of 
springing  it.  A gauge  made  from  drill  rod  is  ground  on 
the  ends  and  then  lapped  in  the  manner  just  explained. 

Flat  gauges  of  the  form  shown  in  Fig.  7 are  to  be  ground 
to  size  after  hardening,  leaving  them  about  .0005  inch  over 
size.  They  are  then  reduced  to  accurate  size  by  careful  oil- 
stoning  with  a very  fine  Arkansas  stone. 

Inside  gauges  that  have  their  measuring  surfaces  parallel 
and  forming  plane  surfaces  are  ground  straight  and  parallel 
in  a surface  grinder.  In  order  to  last  well,  they  should  have 
their  measuring  surfaces  finished  by  lapping.  Evidently, 
lapping  can  only  be  done  either  by  rubbing  the  measuring 
surfaces  on  a lap  charged  with  the  necessary  abrading 
material,  or  by  rubbing  the  lap  over  the  surfaces.  In  either 


arbor  between 


28 


GAUGES  AND  GAUGE  MAKING. 


19 


case,  there  will  be  a tendency  to  lap  the  surfaces  “crown- 
ing.” To  overcome  this  difficulty,  hardened  pieces  of  steel, 


1 Mi 

1 

ill;.  “ „ 

II 

\K~ 

Ik  •••:  _ 

1 IPI, ! 

1 

| Pi- 



Fig.  12. 

as  tf,  a , in  Fig.  12,  may  be  temporarily  fitted  to  the  sides  of 
the  gauge  and  ground 
at  the  same  time  the 
gauge  is  ground.  The 
lapping  operation  will 
then  round  the  sur- 
faces of  these  guard 
pieces,  but  leave  the 
gauge  surfaces  flat. 

When  the  gauge  is 
lapped  to  size,  the 
guard  pieces  are  re- 
moved ' and  thrown 
away. 

Outside  snap 
gauges  can  be  ground 
after  hardening  by 
using  the  method 
shown  in  Fig.  13.  If 
no  suitable  grinding 
machine  is  available, 
any  engine  lathe  fig.  13. 

pan  be  used.  Mount  a thin  and  large  emery  wheel  that  has 


20 


GAUGES  AND  GAUGE  MAKING. 


§ 28 

been  recessed,  as  shown,  on  an  arbor  between  the  lathe  cen- 
ters. Put  a small  pulley  on  the  arbor  and  drive  from  any 
convenient  overhead  pulley.  Clamp  the  gauge  to  the  top 
of  the  slide  rest;  clamp  guard  pieces  of  hardened  steel,  as 
a , a,  to  each  side  of  the  gauge  and  on  the  top  and  bottom ; 
then  grind  by  feeding  in  by  means  of  the  cross-feed  screw. 
Finish  by  lapping  to  size  . and  then  remove  the  guard  pieces. 
With  reasonable  care,  a very  good  job  can  thus  be  made. 


ANGULAR  GAUGES. 

23.  Names  of  Angular  Gauges. — Gauges  for  angular 

measurements  are  made  to  represent  either  definite  angles 
or  tapers,  which  are  the  equivalent  thereof.  When  they 
represent  tapers,  they  are  most  commonly  known  as  taper 
gauges , and  their  size  is  expressed  by  the  taper  in  inches  per 
foot  they  represent.  Angular  gauges  have  their  sizes 
expressed  in  degrees  and  minutes,  although,  occasionally, 
they  receive  a special  name.  Thus,  an  angular  gauge  meas- 
uring a 90°  angle  is  most  commonly  known  as  a try  square; 
a gauge  measuring  an  angle  of  180°  is  familiarly  called  a 
straightedge ; and  a gauge  that  represents  a 60°  angle,  from 
its  most  general  application,  is  best  known  as  a thread  gauge. 

24.  Laying  Out  Angles. — Angular  gauges  may  be 
made  in  different  ways,  according  to  the  degree  of  accuracy 
required.  If  only  a reasonable  degree  of  accuracy  is  required, 
the  given  angle  or  taper  may  be  laid  off  on  a piece  of  sheet 
steel,  which  is  then  filed  to  the  lines  scribed  thereon.  If 
this  method  of  construction  is  considered  accurate  enough, 
an  angle  may  be  laid  off  most  conveniently  by  the  aid  of  a 
table  of  natural  sines  and  tangents.  Scribe  a straight  line, 
as  a in  Fig.  14,  on  the  surface  of  the  piece  of  steel.  Make 
two  very  fine  center-punch  marks,  as  b and  c,  on  this  line 
and  as  far  apart  as  circumstances  permit.  At  c erect  a per- 
pendicular, as  c d.  Measure  the  distance  b e as  accurately 
as  possible  with  a steel  scale,  preferably  with  a decimally 
divided  scale.  From  a table  of  natural  tangents,  take  the 


28 


GAUGES  AND  GAUGE  MAKING. 


21 


tangent  of  the  required  angle  and  multiply  the  distance  b c 
by  this  tangent.  Then,  on  ^ lay  off  as  accurately  as  pos- 
sible the  product  of  be  and  the  tangent,  marking  it  by  a fine 


center-punch  mark,  as  made  on  the  line  c d.  Scribe  a line 
through  b and  e\  the  angle  e be  included  between  the  lines  a 
and  f is  the  required  angle. 


25.  When  the  required  angle  is  greater  than  45°,  it  is 
more  convenient  to  use  the  method  shown  in  Fig.  15.  Scribe 


C.  S.  HI.— $7 


22 


GAUGES  AND  GAUGE  MAKING. 


§28 


the  line  a and  on  it  lay  off  be  as  long  as  convenient.  At  c 
erect  the  perpendicular  line  de.  From  a table  of  natural 
tangents,  take  the  tangent  corresponding  to  one-half  the 
required  angle;  multiply  the  distance  be  by  this  tangent 
and  lay  off  the  distance  thus  found  on  both  sides  of  c,  mark- 
ing it  at  f and  £*.  Join  /"and^to  b by  straight  lines.  The 
angle  fbg  is  then  the  required  angle. 

2f>.  When  the  required  angle  is  greater  than  90°,  instead 
of  laying  off  that  angle,  its  supplement  is  laid  off.  Subtract 

the  required  angle  from 


The  correctness  with  which  an  angle  can  thus  be  pro- 
duced naturally  depends  on  the  skill  of  the  workman  in 
working  to  the  scribed  lines  and  on  the  accuracy  with  which 
they  have  been  located.  As  a general  rule,  it  may  be  stated 
that  a much  greater  degree  of  accuracy  can  be  obtained  by 
this  method  than  is  possible  by  laying  off  angles  with  the 
ordinary  bevel  protractor  made  for  machine-shop  work.  All 
other  factors  remaining  as  before,  the  accuracy  attainable 
will  be  greater  as  the  base  line,  as  be,  Figs.  14  and  15,  or  a e, 
Fig.  16,  is  made  longer. 


TAPER  GAUGES. 

27.  Different  Definitions  of  Taper. — When  an 

angular  gauge  is  ordered  to  represent  a certain  taper  per 
foot,  the  toolmaker  should  find  out  by  inquiry,  first  of  all, 
what  the  person  ordering  the  gauge  understands  by  the 
term  “taper.”  Unfortunately,  the  term  has  no  definite 


GAUGES  AND  GAUGE  MAKING. 


23 


§ 28 

meaning,  being  used  in  different  senses  in  different  locali- 
ties. Referring  to  Fig.  .17  (tf),  the  taper  is  defined  by  some 
as  the  difference  in  diameters  (d—d')  per  foot  of  length,  the 
taper  in  all  cases  being  expressed  in  inches  and  fractional 
parts  of  an  inch.  The  measurements  for  diameter  are  made 
on  lines  perpendicular  to  the  axis,  which  is  also  the  line 
bisecting  the  angle  made  by  the  sides  a b and  e foi  the  taper- 
ing piece.  In  Fig.  17  (b)  the  difference  in  the  radii  (r—r1) 
per  foot  of  length  is  considered  as  the  taper.  In  this  case, 


the  measurements  for  the  taper  are  made  on  lines  perpen- 
dicular to  the  axis,  or  line  bisecting  the  angle  included 
between  a b and  e ft  but  only  to  one  side  of  the  axis.  Evi- 
dently, if  the  taper  is  expressed  in  accordance  with  Fig.  17  (b), 
it  will  be  only  one-half  that  of  Fig.  17  ( a ),  but  yet  the  angle 
included  between  a b and  ef  will  be  the  same  in  either  case. 

When  the  taper  of  flat  work,  as  keys  or  wedges,  is  meas- 
ured, probably  the  most  common  way  is  to  take  one  side,  as 
e Fig.  17  (c),  as  a base  line  and  measure  the  taper  by  the 
difference  (Ji  — h')  in  height  of  perpendiculars,  as  e a and  fb, 
erected  at  the  ends  of  the  base  line.  Many  persons  will 
measure  the  taper  of  flat  work  in  the  manner  shown  in 


24 


GAUGES  AND  GAUGE  MAKING.* 


§28 

Fig.  17  (d).  Here  the  difference  in  height  is  measured  to 
both  sides  of  a line  bisecting  the  angle  included  between  the 
sides  a b and  e /and  on  lines  perpendicular  to  the  bisecting 
line.  This  method  is  the  same  as  that  shown  in  Fig.  17  (a). 
Now,  on  first  thought  it  would  seem,  wheir  comparing  two 
pieces  of  the  same  nominal  taper,  of  which  one  has  been 
measured  according  to  Fig.  17  {c)  and  the  other  according 
to  Fig.  17  (d),  as  if  there  were  no  difference  in  the  angles 
included  between  a b and  e f.  There  is  a decided  difference, 
however,  as  can  be  seen  by  referring  to  Fig.  18.  In  this 


figure,  the  triangle  a f g represents  a taper  of  8 inches  per 
foot  measured  in  accordance  with  Fig.  17  (c)  ; the  tri- 
angle abc  also  represents  a taper  of  8 inches  per  foot,  but 
measured  in  accordance  with  Fig.  17  (d).  An  inspection 
shows  that  there  is  a decided  difference  in  the  angles  e 
and  h. 

28.  Laying;  Out  a Taper  Gauge.  — If  a taper 
gauge  is  to  be  laid  out  on  sheet  steel,  the  method  of  laying 
it  out  naturally  depends  on  the  method  by  which  the  taper 
is  measured.  Suppose  a taper  gauge  is  to  be  made  for  a 
flat  wedge  that  is  three  inches  long  on  one  side  and  1 inch 
high  at  the  thick  end.  The  taper  is  to  be  1 inch  per  foot, 


GAUGES  AND  GAUGE  MAKING. 


25 


§ 28 

and  the  person  ordering  the  gauge  wants  the  taper  to  be 
measured  by  taking  the  measurements  perpendicular  to  one 
side,  that  is,  as  shown  in  Fig.  17  (c).  Then,  before  the  lines 
can  be  scribed  on  a sheet-steel  gauge,  the  height  at  the  thin 
end  of  the  wedge  must  be  calculated.  If  the  taper  is  meas- 
ured as  shown  in  Fig.  17  («),  (c),  or  ( d ),  the  difference  in 
height,  or  in  diameter  in  case  of  round  work,  may  be  found 
by  the  following  rule  : 

Rule. — Divide  the  given  length  by  12  and  multiply  by  the 
taper. 

When  applying  this  rule  to  a taper  measured  as  in 
Fig.  17  ( d ),  it  is  to  be  observed  that  it  gives  the  difference 
in  height  of  lines  the  given  distance  apart  and  perpendicular 
to  the  line  bisecting  the  angle,  on  which  line  the  given  dis- 
tance is  measured.  If  the  taper  has  been  measured  as  shown 
in  Fig.  17  ( b ),  the  result  given  by  the  rule  must  be  doubled 
to  obtain  the  difference  in  diameters. 

Applying  the  rule  given,  we  get,  for  the  case  under  con- 

3x1 

sideration,  \ inch  as  the  difference  between  the  large 

and  small  ends.  Then,  the  small  end  is  evidently  1 — \ 
==  J inch  high.  The  laying  out  of  the  gauge  is  now  a simple 
matter.  Draw  a straight  line  3 inches  long  ; erect  perpen- 
diculars at  the  ends  f inch  and  1 inch  high,  and  join  the 
ends  of  the  perpendiculars  by  a straight  line.  Then  cut  out 
the  metal  and  file  to  the  lines. 

When  the  taper  has  been  measured  in  accordance  with 
Fig.  17  (a)  or  (d),  scribe  a straight  line  of  the  required 
length  and  at  its  ends  erect  perpendiculars.  Lay  off  half  the 
heights  (or  diameters)  on  each  side  of  the  line  first  scribed 
and  join  the  ends  of  the  perpendiculars  by  straight  lines. 

When  making  a sheet-metal  taper  gauge  or  angular  gauge, 
it  is  not  advisable  to  cut  out  the  metal  with  a chisel,  since 
this  may  spring  it  considerably  out  of  true.  It  is  better  to 
saw  out  the  metal  with  a hack  saw,  or  drill  a row  of  holes 
close  together  and  then  cut  through  the  metal  remaining 
between  the  holes  with  a saw  or  file. 


26 


GAUGES  AND  GAUGE  MAKING. 


§28 


29.  Originating  Tapers  and  Angles.  — The  most 

accurate  way  of  originating  a taper  or  an  angle  (except  a 
60°,  90°,  and  180°  angle)  is  shown  in  Fig.  19.  The  same 


O' 


d 


0 


] 


principle  that  is  involved  in  originating  a taper  or  angle 
allows  the  same  method  to  be  used  to  measure  accurately  a 
taper  or  angle  whose  exact  measure  is  not  known. 

In  Fig.  19,  a and  b are  two  straightedges  that  are  ground 
and  lapped  as  nearly  true  as  possible.  They  are  so  mounted 
in  a suitable  frame  that  they  can  readily  be  shifted  and  then 
locked  rigidly.  Steel  disks  c and  d ground  and  lapped  truly 
cylindrical  and  of  any  convenient  diameter  are  placed 
between  the  straightedges  and  in  contact  with  them.  Then, 
the  diameters  of  the  disks  and  their  center-to-center  dis- 
tance, all  of  which  dimensions  can  be  accurately  measured, 
definitely  determine  the  taper  included  between  the  straight- 
edges, or  the  angle,  and  these  data  can  then  be  calculated 
by  the  following  rules: 

30.  If  the  taper  is  measured  in  accordance  with  the 
method  shown  in  Fig.  17  (a)  and  ( d ),  the  taper  included 
between  the  straightedges  is  calculated  as  follows: 

Rule. — Divide  the  difference  in  the  diameters  of  the  disks 
by  twice  their  distance  from  center  to  center . From  a table 


GAUGES  AND  GAUGE  MAKING. 


27 


§ *8 

of  natural  sines , take  the  angle  corresponding  to  the  quo- 
tient. Then,  in  a table  of  natural  tangents , find  the  tan- 
gent corresponding  to  this  angle.  Multiply  the  tangent 
by  2f 

If  the  taper  is  measured  in  accordance  with  Fig.  17  (b), 
divide  by  2 the  result  obtained  by  the  rule  just  given. 

Example. — The  disks  being  2 inches  and  4 inches  in  diameter,  and 
their  center- to-center  distance  being  4.5  inches,  (a)  what  is  the  taper 
in  inches  per  foot  if  measured  in  accordance  with  Fig.  17  ( a ) or  (d)7 
{{?)  What  is  the  taper  if  measured  as  in  Fig.  17  (6)  ? 

4 — 2 

'Solution. — ( a ) Applying  the  rule  given,  we  get  Q ^ ^ ^ = .22222  as 

the  sine.  The  nearest  angle  is  12°  50'.  The  tangent  corresponding  to 
this  angle  is  .22781.  Then,  the  taper  is  .22781  X 24  = 5.4674  in.  per  ft. 

Ans. 

(b)  Dividing  answer  in  {a)  by  2,  we  get  5.4674  -f-  2 = 2.7387  in. 
per  ft.  Ans. 

31.  If  the  taper  is  measured  according  to  Fig.  17  (< c ),  use 
the  following  rule: 

Rule. — Divide  the  difference  in  the  diameters  of  the  disks 
by  twice  their  distance  from  center  to  center.  Find  the 
corresponding  angle  in  a table  of  sines ; double  the  angle 
thus  found  and  find  its  tangent.  Multiply  the  tangent  by  12. 

Example. — Taking  the  same  values  as  in  the  previous  example,  what 
will  be  the  taper  per  foot  if  measured  in  accordance  with  Fig.  17  (c)  ? 

4 — 2 

Solution. — Applying  the  rule  just  given,  we  get  Q ^ — - = .22222  as 

the  sine.  The  nearest  angle  is  12°  50'.  Doubling  this  angle,  we  get 
25°  40'.  The  corresponding  tangent  is  .48055.  Then,  the  taper  is 
.48055  X 12  = 5.7666  in.  per  ft.  Ans. 

32.  When  the  taper  in  inches  per  foot  is  given,  to  find 
the  diameters  of  the  disks  and  their  center-to-center  distance : 

Rule. — Assume  the  diameters  of  the  disks  as  dictated  by 
judgment.  Divide  the  taper  by  2k,  if  the  taper  is  measured 
in  accordance  with  Fig.  17  (a)  or  (d).  If  measured  in 
accordance  with  Fig.  17  (b),  divide  the  taper  by  12.  From 
a table  of  natural  tangents , find  the  angle  correspondmg  to 
the  quotient.  Then , from  a table  of  natural  sines , take 


28 


GAUGES  AND  GAUGE  MAKING. 


§28 


the  sine  corresponding  to  the  angle.  Finally,  divide  the 
difference  in  the  diameters  of  the  disks  by  twice  the  sine. 

Example. — If  a taper  of  2 inches  per  foot  is  to  be  originated,  what 
must  be  the  center-to-center  distance  of  the  disks,  assuming  them  to 
be  2 inches  and  3.5  inches  in  diameter,  {a)  if  the  taper  is  measured 
according  to  Fig.  17  (a)  and  (d)  ? (b)  if  the  taper  is  measured  accord- 
ing to  Fig.  17  (b)  ? 

Solution. — (a)  By  the  rule  just  given,  2 24  — .08333.  The  nearest 

angle  corresponding  to  this  tangent  is  4°  46'.  The  sine  of  this  angle 

is  .0831.  Then,  = 9.0253  in.  Ans. 

.Uool  X " 

(b)  2 -r-  12  = .16666.  The  nearest  angle  corresponding  to  this 

g <5 2 

tangent  is  9°  28'.  The  sine  of  this  angle  is  .16447.  Then,  ^447 
= 4.560  in.  Ans. 

33.  When  the  taper  is  given  in  accordance  with  Fig.  1 7 (c), 
assume  the  diameters  of  the  disks  as  dictated  by  judgment. 
Then,  to  find  their  center-to-center  distance : 

Rule. — Divide  the  taper  by  12.  From  a table  of  natural 
tangents,  find  the  corresponding  angle.  Find  the  sine  of 
half  the  angle  thus  found,  and  divide  the  difference  in  the 
diameters  of  the  disks  by  double  the  sine. 

Example. — If  the  disks  are  2 inches  and.  3.5  inches  in  diameter,  what 
must  be  their  center-to-center  distance  to  produce  a taper  of  2 inches 
per  foot  measured  in  accordance  with  Fig.  17  (c)  ? 

Solution.— Applying  the  rule  just  given,  2 12  = .16666.  The 

nearest  angle  corresponding  to  this  tangent  is  9°  28'.  Half  of  this 

g g 2 

angle  is  4°  44'.  The  sine  corresponding  is  .08252.  Then,  ■ ■ ■ ‘ ■ 

. 082o2  X 2 

= 9.0887  in.  Ans. 

34.  It  occasionally  happens  that  it  is  desired  to  find  the 
angle  included  between  the  lines  ab  and  ef,  Fig.  17,  when 
the  taper  is  given.  Then,  if  the  taper  is  measured  as  in 
Fig.  17  (a)  and  (d) : 

Rule. — Divide  the  taper  by  21/..  Look  up  this  value  in  a 
table  of  natural  tangents  and  double  the  corresponding  angle. 

Example. — What  angle  corresponds  to  a taper  of  3 inches  per  foot, 
if  the  taper  is  measured  as  in  Fig.  17  (a)  and  ( d ) ? 


28 


GAUGES  AND  GAUGE  MAKING. 


29 


Solution. — By  the  rule  just  given,  3 -4-  24  = .125.  The  nearest 
angle  is  7°  8'  and  twice  this  angle  is  14°  16'.  Ans. 

35.  If  the  taper  is  measured  as  in  Fig.  17  (b) : 

Rule. — Divide  the  taper  by  12.  Find  the  corresponding 
angle  in  a table  of  natural  tangents  and  double  it. 

Example. — A taper  of  3 inches  per  foot  is  given  in  accordance  with 
Fig.  17  ( b ).  What  is  the  angle  ? 

Solution. — 3-5-12  = .25.  The  nearest  angle  is  14°  2'.  Then,  the 
required  angle  is  14°  2'  X .2  = 28°  4'.  Ans. 

36.  If  the  measurement  for  taper  is  made  according  to 
Fig.  17  (c): 

Rule. — Divide  the  taper  by  12.  From  a table  of  natural 
tangents , find  the  angle  corresponding  to  the  quotient. 

Example. — What  angle  corresponds  to  a taper  of  3 inches  per  foot 
measured  as  in  Fig.  17  (c)  ? 

Solution. — 3 12  = .25.  The  nearest  angle  = 14°  2'.  Ans. 

37.  When  the  straightedges  of  Fig.  19  are  to  be  set  to  a 
.given  angle  by  means  of  the  disks,  their  center-to-center 
distance  may  be  found  as  follows: 

Rule. — Take  the  sine  of  half  the  angle  from  a table  of 
natural  sines.  Divide  the  difference  in  the  diameters  of  the 
disks  by  double  the  sine.  ' 

Example. — If  an  angle  of  20°  is  to  be  originated,  and  the  disks  are 
2 inches  and  4 inches  in  diameter,  what  must  be  their  center-to-center 
distance  ? 

Solution.—  20°  A-  2 = 10°.  The  sine  of  10°  = .17365.  Then, 

2 - = 5.7587  in.  Ans. 

. 1736o  X 2 

38.  In  case  it  is  desired  to  measure  the  angle  included 
between  the  straightedges: 

Rule. — Divide  the  difference  in  the  diameters  of  the  disks 
by  twice  their  center-to-center  distance.  From  a table  of 
natural  sines y take  the  angle  corresponding  to  the  quotient 
and  double  it. 


GAUGES  AND  GAUGE  MAKING. 


30 


§ 28 


Example. — The  disks  being  2 inches  and  5 inches  in  diameter,  and 

5 inches  from  center  to  center,  what  is  the  angle  included  between  the 
straightedges  ? 

pj 2 

Solution. — 1 = — .3.  The  nearest  angle  is  17°  27'.  Then, 

"X  5 

17°  27'  X 2 = 34°  54'.  Ans. 

39.  If  the  center-to-center  distance  calculated  by  any 
of  the  rules  previously  given  is  less  than  half  the  sum  of  the 
diameters  of  the  disk,  either  one  of  the  disks  must  be  made 
smaller  or  the  other  one  larger,  and  the  calculation  repeated 
until  the  distance  becomes  larger  than  half  the  sum  of  the 
diameters. 

The  center-to-center  distance  can  be  measured  in  two 
ways:  Measure  the  distance  between  the  disks  and  add  half 
the  sum  of  the  diameters;  or  measure  the  distance  over  the 
outside  of  the  disks  and  subtract  half  the  sum  of  the 
diameters. 

In  order  to  originate  an  accurate  taper  gauge  for  flat 
work,  the  device  shown  in  Fig.  19  is  set  to  the  given  taper. 
An  inside  gauge  is  then  fitted  to  it,  continuing  the  fitting 
until  no  daylight  can  be  seen,  when  the  gauge  is  placed 
between  the  straightedges.  The  outside  gauge  is  then  care- 
fully fitted  to  the  inside  gauge  just  made;  it  thus  becomes 
a duplicate  of  the  taper  (or  angle)  included  between  the 
straightedges.  If  necessary,  either  one  of  the  pair  of 
gauges  is  kept  as  a reference  gauge  to  show  wear  of  the 
other. 

Taper  gauges  for  round  work  (conical  work)  are  made 
both  as  inside,  or  plug,  and  as  outside  gauges.  The  device 
is  first  set  to  the  angle  (or  taper)  required;  the  plug  gauge 
is  then  ground  until  no  daylight  can  be  seen,  when  it  is 
placed  between  the  straightedges.  The  outside,  or  ring, 
gauge  is  next  ground  until  it  exactly  fits  the  plug  gauge, 
using  the  finest  grade  of  Prussian  blue  as  a marker  to  show 
the  fit. 

40.  Originating  a 60°  Angle. — A 60°  angle  can  be 

originated  most  readily  by  the  method  first  used  by  Pratt 

6 Whitney  for  originating  a standard  with  which  thread 


GAUGES  AND  GAUGE  MAKING. 


31 


§ 28 

gauges  could  be  compared.  The  principle  made  use  of  is 
that  in  an  equilateral  triangle  each  interior  angle  is  equal  to 
60°.  Then,  if  three  bars  are  made,  as  a , b,  and  c,  Fig.  20, 


each  of  them  exactly  equal  to  the  other,  and  with  the  holes 
the  same  distance  apart  and  in  the  same  relative  positions 
in  regard  to  the  sides,  the  center  lines  of  these  bars  when 
connected  by  pins  passing  through  the  holes  will  form  an 
equilateral  triangle;  and,  as  the  inside  and  outside  surfaces 
of  the  bars  are  parallel  to  the  center  line,  all  angles  included 
between  the  inside  or  outside  of  the  bars  will  be  60°  angles. 


TRY  SQUARES. 

41.  Making  a Try  Square. — A 90°  angle  may  be 
originated  in  several  ways.  The  first  method  here  given 
will  produce  two  try  squares,  both  of  which,  if  skilfully 
made,  will  be  about  as  correct  as  it  is  possible  to  produce 
them.  There  is  one  appliance  necessary,  however,  on  the 
truth  of  which  the  correctness  of  the  try  squares  will  depend. 
This  appliance  may  be  either  a straightedge  or  a surface 
plate;  eithe'r  one  of  them  may  be  used,  but  it  must  be  as 
true  as  skill  and  ingenuity  can  make  it.  When  making  try 
squares,  it  is  easiest,  as  a general  rule,  to  do  all  truing  on 


32  GAUGES  AND  GAUGE  MAKING.  § 28 

the  blade,  since  the  amount  of  metal  to  be  removed  is  usu- 
ally quite  small. 

To  make  the  try  squares,  finish  the  stocks  by  grinding 
their  top  and  bottom  surfaces  parallel  and  as  nearly  plane  as 
possible.  A surface-grinding  machine  is  invaluable  for  this 
work.  If  it  must  be  done  by  hand,  great  care  is  required  to 
make  as  good  a job  of  it  as  can  be  done  by  the  surface- 
grinding machine.  The  two  stocks  having  been  finished, 


fig.  21. 


insert  and  fasten  the  blades,  which  have  been  previously 
ground  true  and  parallel.  Select  the  square  that  seems  to 
be  the  most  accurate,  using  judgment  in  the  selection.  Fit 
the  other  square  to  it  until  they  fit  either  way,  when  stock 
is  placed  against  stock  and  blade  against  blade,  as  shown  in 
Fig.  21  (a). 

The  two  squares  are  now  duplicates  of  each  other,  but  it 
is  not  known  as  yet  whether  the  angle  between  stock  and 
blade  is  correct,  or  if  not,  which,  way  the  squares  are  out. 
To  test  this,  place  both  squares  blade  to  blade  on  a surface 
plate  or  straightedge,  as  shown  in  Fig.  21  (b),  and  with  tbe 
stocks  resting  on  the  surface  plate  or  straightedge,  observe 
if  the  blades  are  in  contact  with  each  other  throughout 
their  length.  If  they  touch  so  that  no  daylight  can  be  seen 
between  them,  both  squares  are  correct.  Suppose,  however, 
that  there  is  an  opening  at  the  top,  as  shown  in  Fig.  21  (b). 
Then,  this  shows  that  the  angle  between  stock  and  blade  is 
smaller  than  90° ; conversely,  if  the  opening  is  at  the  bottom, 


28 


GAUGES  AND  GAUGE  MAKING. 


33 


the  angle  is  larger  than  90°.  Next,  take  one  of  the  squares 
and  shift  its  blade  one-half  the  amount  indicated.  If  the 
shifting  must  be  done  by  grinding  the  blade,  grind  off  the 
probable  amount  on  one  side  and  then  make  the  other  side 
absolutely  parallel  to  it.  Now,  fit  the  second  square  to  the 
first  square  just  corrected;  place  them  blade  to  blade  again 
on  the  surface  plate  or  straightedge,  and  repeat  the  cycle  of 
operations  until  the  squares  will  fit  when  placed  stock  to 
stock  and  blade  to  blade.  Both  squares  will  then  be  correct. 

42.  Testing  Try  Squares. — If  a try  square  is  to  be 
tested  for  correctness,  the  most  obvious  way  is  to  compare 
it  with  a test,  or  reference,  try 
square.  If  there  is  none  at  hand 
and  circumstances  permit,  an  ex- 
cellent substitute  for  a test  square 
may  be  made  as  shown  in  Fig.  22. 

Take  a piece  of  good  machinery 
steel  or  well-annealed  tool  steel 
having  a length  not  less  than  the 
length  of  the  blade  of  the  try 
square,  and  a diameter  of  not  more 
than  the  inside  length  of  the  stock. 

Recess  one  end  about  y1^  inch  deep, 
making  the  diameter  of  the  recess 
about  ^ inch  less  than  the  outside 
diameter.  Turn  the  outside  true 
and  straight;  slightly  bevel  the  edge  at  the  recessed  end 
and  then  finish  by  grinding  and  lapping  between  dead 
centers,  and  finally,  without  previous  removal  from  the 
grinding  machine,  accurately  face  the  annular  ring  at  the 
cupped  end.  Obviously,  if  the  cylinder  is  finished  true  and 
straight,  the  angle  between  the  plane  of  the  ring  and  the 
cylindrical  surface  is  a right  angle. 

Since  there  should  not  be  any  difficulty  in  lapping  the 
device  straight  within  a variation  of  .00002  inch,  and  since 
the  ring  can  be  ground  to  be  in  a plane  perpendicular  to 
the  axis  within  an  insensible  amount  of  variation,  it  is 


Fig.  22. 


34 


GAUGES-  AND  GAUGE  MAKING. 


28 


believed  that  this  is  the  most  accurate  method  of  originating 
a 90°  angle  that  has  been  devised.  This  device  may  be 
used  for  testing  the  truth  of  the  inside  and  outside  angles  of 
a try  square.  To  test  the  inside  angle,  the  try  square  is 
applied  directly  to  the  device,  as  shown  in  Fig.  22.  To  test 
the  outside  angle,  the  device  and  try  square  are  both  placed 
on  a surface  plate  and  brought  in  contact  with  each  other. 
Practical  considerations  will  fix  a limit  within  which  this 
device  can  be  used.  These  considerations  are  the  weight 
allowable  and  the  facilities  for  grinding  and  lapping;  from 
these,  the  toolmaker  can  readily  determine  the  limits  within 
which  the  method  just  given  is  applicable. 

A simple  method  of  testing  try  squares  intended  for  com- 
paratively rough  work  is  shown  in  Fig.  23.  One  edge  of  a 


Fig.  23. 


wooden  or  metal  plate  that  forms  a fair  approximation  to  a 
plane  surface  is  trued  up  to  a straightedge.  The  stock  of 
the  square  is  then  placed  against  this  edge  and  a faint  line  is 
scribed  along  the  blade.  The  square  is  now  reversed,  as 
shown  by  the  dotted  lines;  if  the  blade  coincides  with  the 
scribed  line,  the  square  is  true.  If  the  blade  is  farther 
away  from  the  line  at  the  top  than  it  is  near  the  stock,  it 
shows  that  the  angle  is  less  than  90° ; conversely,  if  it  is  far- 
ther away  near  the  stock  than  at  the  end  of  the  blade,  the 


28 


GAUGES  AND  GAUGE  MAKING. 


35 


angle  is  larger  than  90°.  This  method  shows  double  the 
error. 

43.  Making  a Test  Block  for  a Square. — A refined 
method  of  making  a test  block  for  testing  try  squares  was 
made  public  in  1896  by  Mr.  G.  A.  Bates,  an  expert  tool- 
maker  of  Brooklyn,  New  York.  The  construction  of  the 
test  block  is  shown  in  Fig.  24.  It  consists  of  a rectangular 


cast-iron  frame  a,  which  has  a groove  of  rectangular  cross- 
section  all  around  its  circumference.  The  sides  of  the  groove 
are  finished  straight  and  parallel  by  planing  or  milling.  Four 
separate  blades,  as  l?,  I?,  are  closely  fitted  to  the  groove  in 
the  frame;  they  are  connected  to  the  frame  by  well-fitted 
fulcrum  pins  c , c located  near  one  end  of  the  blades.  The 
end  of  the  blades  opposite  the  pins  is  connected  to  the  frame 
by  small  bolts,  as  d,  which  fit  tapped  holes  in  the  blades 
and  pass  through  a clearance  hole  in  setscrews,  as  e\ 
these  setscrews  are  fitted  to  holes  tapped  in  the  frame. 


36 


GAUGES  AND  GAUGE  MAKING. 


§ 28 

Evidently,  by  moving  the  setscrews  and  setting  up  the 
locking  bolts,  each  blade  can  be  rotated  slightly  around  its 
fulcrum  and  then  locked  in  position.  While  the  blades  are 
shown  as  having  a T shape,  they  may  be  made  rectangular 
as  well,  or,  if  considered  desirable,  the  edges  projecting 
from  the  frame  may  be  thinned  down  by  beveling.  The 
measuring  surfaces  of  the  blades  are  filed  and  scraped  so  as 
to  make  true  plane  surfaces,  scraping  them  either  to  a true 
surface  plate  or  to  a true  straightedge.  It  should  be 
remembered  that  the  value  of  the  test  block  depends,  to  a 
large  extent,  on  the  straightness  of  the  measuring  edges; 
hence,  these  must  be  made  as  perfect  as  skill  and  ingenuity 
can  make  them.  The  setscrews  e and  locking  bolts  d should 
have  a rather  fine  pitch  of  thread,  say  40  threads  per  inch, 
or  even  finer,  as  a sensitive  adjustment  can  then  be  readily 
obtained.  The  screws  e must  be  a good  snug  fit,  since  any 
looseness  will  destroy  the  value  of  the  testing  block. 


44.  I n order  to  set  the  test  block  so  that  any  two 
adjacent  blades  are  at  a right  angle  to  each  other,  a tem- 
porary try  square  is  made  out  of 
sheet  iron  or  sheet  steel.  A very 
convenient  form  of  such  a try 
square  is  shown  in  Fig.  25.  In- 
stead of  finishing  the*  inside  of 
the  blades  throughout  their 
length,  they  are  cut  away  in 
order  to  leave  the  small  projec- 
tions shown.  When  any  change 
is  required,  it  is  easier  to  dress 
down  the  projections  than  to 


Fig.  25. 

refinish  the  blade  throughout  its  length 

The  try  square  having  been  finished  until  it  is  believed  to 
be  fairly  accurate,  it  is  applied  to  two  adjacent  blades  of  the 
test  block.  One  of  these  blades  is  then  adjusted  until  both 
blades  fit  the  temporary  try  square.  Suppose  the  try  square 
has  been  used  on  the  top  and  right-hand  blade  of  the  test 
block  and  that  the  top  blade  has  been  adjusted.  Then,  it  is 


28 


GAUGES  AND  GAUGE  MAKING. 


37 


next  applied  to  the  top  and  left-hand  blade ; the  latter  is  now 
adjusted  to  fit  the  try  square.  The  bottom  blade  is  finally 
adjusted  from  the  left-hand  blade  and  to  the  try  square;  on 
applying  the  try  square  to  the  bottom  and  right-hand  blade, 
any  error  of  the  try  square  will  be  shown  multiplied  four 
times.  The  try  square  is  now  corrected  and  the  blades  of 
the  test  block  readjusted.  These  operations  are  repeated 
until  the  try  square  fits  exactly  all  around  the  test  block; 
when  this  is  the  case,  any  two  adjacent  blades  of  the  test 
block  are  at  a right  angle  to  each  other,  and  the  try  square 
is  also  truly  square. 


STRAIGHTEDGES. 

45.  Originating  a Straightedge.  — A correct 
straightedge  can  be  produced  either  by  fitting  it  to  an 


absolutely  correct  surface  plate,  or  it  can  be  originated  in 
accordance  with  the  following  axiom : Three  straightedges 
cannot  fit  one  another  unless  all  three  are  straight.  The 


C.  S.  Ill— 38 


38 


GAUGES  AND  GAUGE  MAKING. 


28 


facilities  at  command  of  the  toolmaker  will  determine  which 
method  is  to  be  used. 

Three  straightedges  having  been  finished  all  over,  select 
one  of  these  as  a trial  straightedge ; perferably  select  the 
one  that  is  believed  to  be  nearest  correct.  Mark  this  i,  and 
mark  the  two  others  2 and  3,  respectively.  Carefully  fit 
straightedges  2 and  3 to  i,  as  shown  in  Fig.  26,  until  no 
daylight  can  be  seen  between  1 and  2 and  1 and  3 when 
holding  them  up  against  a strong  light.  This  done,  place  2 
and  3 together,  as  shown  in  the  illustration.  Any  deviation 
from  a straight  line  will  now  show  double.  Take  one  of 
these  two  equal  straightedges,  say  2 , and  reduce  its  error. 
Use  this  as  a trial  straightedge  and  fit  1 and  3 to  it.  Place  1 
and  3 together,  observe  the  error,  and  reduce  it  on  number  3. 
Use  3 as  a trial  straightedge  and  fit  1 and  2 to  it.  Place  1 
and  2 together,  reduce  the  error  of  1 and  use  it  as  a trial 
straightedge  once  more,  fitting  "2  and  3 to  it.  Repeat  these 
operations  until  all  three  straightedges  fit  one  another ; all 
three  will  then  be  straight. 

It  is  not  possible  to  use  fewer  than  three  straightedges, 
since  two  straightedges  can  be  perfectly  fitted  to  each  other, 
and  be  a perfect  fit  on  each  other  in  any  position  in  which 
they  are  placed,  without  being  anywhere  near  true. 

46.  Forms  of  Straightedges. — Straightedges  are 
made  in  various  forms.  Most  generally  they  are  made  rect- 
angular in  cross-section,  and  of  uniform  width  throughout 
their  length.  They  must  then  be  made  wide  and  thick 
enough  to  give  stiffness  sufficient  to  prevent  any  sensible 
deflection  with  reasonable  care  in  their  use.  If  their  width 
is  made  equal  to  .12  times  the  length  increased  by  .6  inch, 
and  their  thickness  equal  to  .005  times  the  length  increased 
by  .05  inch,  a satisfactory  degree  of  stiffness  can  usually  be 
obtained,  provided  the  length  of  the  straightedge  does  not 
exceed  40  inches.  Since  toolmakers  are  by  no  means  agreed 
upon  what  deflection  is  permissible,  the  proportions  here 
given  are  to  be  considered  as  those  that  we  think  will  give 
satisfactory  results. 


§28 


GAUGES  AND  GAUGE  MAKING. 


39 


Straightedges  become  more  sensitive,  that  is,  they  will 
more  readily  show  a minute  deviation,  as  their  measur- 
ing edge  is  made  narrower.  They  are  most  sensitive  when 
made  so  that  they  touch  the  work  merely  along  a line;  i.  e., 
when  they  are  in  line  contact  with  it  instead  of  in  surface 
contact.  Then,  carrying  out  this  idea,  a straightedge  may 
be  given  sufficient  thickness  and  width  in  order  to  give 
stiffness,  and  it  may  be  beveled  at  its  measuring  edge  in 
order  to  give  sensitiveness.  Beveled  straightedges  are  usu- 
ally beveled  sufficient  to  leave  the  measuring  edge  y1-^  inch 
wide.  When  beveled  off  more  than  that,  the  cross-section 
bears  a close  resemblance  to  that  of  a knife  blade,  and  the 
straightedge  is  then  called  a knife-edge  straightedge. 

A very  satisfactory  cross-section  of  a knife-edge  straight- 
edge is  that  adopted  by  Pratt  & Whitney  and  shown  in 
Fig.  27  («).  This  form  combines 
stiffness,  lightness,  and  convenience 
of  handling.  The  more  common 
form  is  shown  in  Fig.  27  (b) ; it  is 
simply  beveled  on  both  sides  to  give 
a narrow  edge.  In  both  forms  of 
knife-edge  straightedges,  the  actual 
testing  edge  a has  a semicircular 
cross-section;  in  other  words,  the 
testing  edge,  instead  of  forming  a 
plane  surface,  forms  part  of  a cylin- 
drical surface.  When  thus  made, 
they  can  be  held  at  a slight  angle  to 
the  work,  without  in  any  way  interfering  with  the  correct- 
ness of  the  measurement.  Hence,  they  are  more  easily 
used  than  straightedges  in  which  the  testing  edge  forms 
a plane  surface;  these  must  be  held  so  that  the  testing 
surface  is  in  contact  all  over  with  the  surface  to  be  tested, 
for  if  canted  over  so  that  one  edge  of  the  testing  surface 
is  in  contact  with  the  work,  a wrong  indication  will  be  given 
if  that  edge  should  be  out  of  true.  As  a general  rule,  in 
making  straightedges  with  a plane-surface  testing  edge,  little 
attention  is  paid  to  making  the  bounding  edges  of  the  testing 


40 


GAUGES  AND  GAUGE  MAKING. 


28 


surface  absolutely  straight;  this  would  add  considerably  to 
the  cost  without  gaining  any  particular  advantage.  Besides, 
the  sharp  edges  would  rapidly  wear  out  of  true. 

Knife-edge  straightedges  cannot  be  very  readily  originated 
by  making  three  fit  one  another.  The  reason  is  that  it  is 
practically  impossible  to  hold  two  of  them  together  so  as  to 
be  in  contact  all  along.  On  account  of  this  difficulty,  knife- 
edge  straightedges  are  usually  fitted  to  a straightedge  hav- 
ing a plane-surface  testing  edge,  or  to  an  accurate  surface 
plate. 


47.  Hardening  Straightedges. — Straightedges  in- 
tended for  work  in  the  shop  are  usually  hardened  on  the 
testing  edge,  and  occasionally  all  over.  The  object  of 
hardening  is  to  reduce  the  liability  of  wear.  Since  the 
hardening  process  sets  up  severe  internal  stresses,  which  are 
gradually  released  by  the  aging  of  the  steel,  hardened 
straightedges  will  occasionally  become  crooked  and  require 
refitting.  If  the  edge  alone  is  hardened  and  the  back  is  left 
soft,  this  change  of  shape  will,  as  a general  rule,  be  small 
enough  to  be  negligible.  Straightedges  intended  for  refer- 
ence only,  i.  e.,  for  testing  working  straightedges,  may  be 
left  soft;  large  straightedges  must  usually  be  left  soft  on 
account  of  the  difficulty  of  hardening. 

To  harden  a straightedge  on  the  edge  only,  place  it 
between  iron  bars  clamped  to  it,  leaving  the  edge  exposed. 
Heat  evenly  all  over  and  then  quench.  The  iron  bars  pre- 
vent the  water  from  coming  in  contact  with  the  back  and 
sides,  which  are  consequently  left  soft. 

48.  Finishing  the  Testing  Edge  of  a Straight- 
edge.—To  make  a straightedge  with  a plane-surface  test- 
ing edge,  it  should  be  ground  as  nearly  straight  as  possible 
on  a surface  grinder,  if  hardened,  and  then  finished  by 
stoning  and  lapping.  If  left  soft,  it  is  finished  by  filing, 
scraping,  and  lapping.  The  straightedge  having  been 
finished  very  nearly  true  by  filing  with  a dead  smooth  file, 
§craping  is  begun,  A neat  device  for  scraping,  and  one  that 


GAUGES  AND  GAUGE  MAKING. 


41 


§ 28 

has  proved  very  useful  in  this  connection,  is  shown  in 
Fig.  28.  For  want  of  a better  name,  and  from  its  resemblance 
to  the  carpenter’s  plane,  it  may  be  called  a scraping  plane. 
As  shown  in  the  figure,  it  consists  of  a body,  one  side  of 
which,  as  b,  is  finished  by  planing  to  suit  the  shape  of  the 
straightedge  that  it  is  intended  for.  The  scraping  tool  is 
set  so  that  its  cutting  edge  is  at  an  angle  of  about  G0°  with 
the  line  of  motion  of  'the  plane;  it  will  then  take  a shaving 
cut.  The  edge  of  the  scraping  tool  slightly  projects  beyond 
the  surface  a , say  about  .0005  inch.  It  is  stoned  to  a very 
keen  edge,  as  nearly  straight  as  possible;  if  made  with  a 
triangular  cross-section  of  cutting  edge,  as  shown,  it  will 


cut  both  ways,  and  make  a very  good  job  if  supplied  with 
plenty  of  lard  oil  and  kept  sharp.  Suppose  now  that  the 
plane  is  held  with  its  surface  b against  the  side  of  the  straight- 
edge, and,  with  the  scraper  resting  on  the  testing  edge,  is 
moved  back  and  forth.  Then,  it  follows  that,  the  scraper 
being  prevented  from  canting  over  to  one  side  or  the  other, 
the  angle  between  the  side  of  the  straightedge  and  its  meas- 
uring edge  will  be  constant  throughout  the  length. 

In  the  illustration,  the  scraping  tool  is  shown  as  being 
held  in  place  by  friction;  if  well  fitted  to  the  sides  of  the 
slot,  this  will  be  sufficient.  If  considered  necessary,  it  may 


42 


GAUGES  AND  GAUGE  MAKING. 


28 


be  held  in  place  by  a key,  or  by  screws;  adjusting  screws  for 
setting  it  out  may  also  be  provided. 

For  the  final  finishing  by  lapping,  a small  L-shaped  piece 
of  cast  iron  may  be  provided.  If  the  lapping  is  then  done 
with  one  leg  of  the  lap  resting  against  the  side  of  the 
straightedge,  the  lap  cannot  be  canted  to  one  side  or  the 
other,  and,  consequently,  a good  job  can  be  done  more 
rapidly  than  could  be  done  otherwise. 

Knife-edge  straightedges,  while  the  most  sensitive  straight- 
edges that  have  been  devised,  are,  at  the  same  time,  the 
most  difficult  ones  to  make.  After  grinding  them  as  nearly 
straight  and  true  as  circumstances  permit,  they  must  be 
finished  by  oilstoning  with  a very  fine  Arkansas  oilstone, 
frequently  comparing  them  with  a plane-surface  straight- 
edge. No  special  directions  that  could  be  given  will  make 
their  production  an  easy  matter  ; it  is  a matter  of  patiently 
stoning  down  the  high  spots  until  the  knife  edge  fits  the 
reference  straightedge  all  along  at  any  angle  within  range 
at  which  it  may  be  held. 

Very  large  straightedges,  say,  above  40  inches  long,  are 
rarely  made  as  knife-edge  straightedges ; the  usual  plan  is 
to  make  them  in  the  form  of  a narrow  surface  plate  and  of 
cast  iron.  They  may  have  a T shape,  with  a rib  of  ample 
depth  and  thickness  to  prevent  deflection.  Straightedges 
of  this  form  are  originated  in  the  same  manner  as  surface 
plates  ; one  being  kept  as  a reference  straightedge,  others 
may  be  made  from  it  by  comparison. 


SPECIAL  GAUGES. 

49.  Where  a large  number  of  pieces  are  to  be  made 
interchangeable,  this  quality  can  only  be  preserved  by 
limit  gauges  so  constructed  as  to  caliper  the  piece  in  all 
essential  directions.  In  some  cases,  one  set  of  limit  gauges 
will  be  sufficient;  in  others  again,  two  or  more  sets  may 
be  required  owing  to  the  difficulty,  if  not  impossibility,  of 
gauging  the  work  all  over  in  one  operation.  Owing  to  the 


28 


GAUGES  AND  GAUGE  MAKING. 


43 


infinite  number  of  shapes  possible,  no  definite  rules  can  be 
given  as  to  the  construction  of  special  gauges  ; each  case 
must  be  treated  on  its  own  merits,  and  the  toolmaker  must 
exercise  his  ingenuity  as  to  the  best  way  of  designing  and 
constructing  the  gauges.  The  only  general  directions  that 
can  be  given  are  to  make  the  gauges  as  simple,  durable,  and 
capable  of  exact  duplication  as  circumstances  will  permit. 
Furthermore,  always  provide  means  of  getting  the  work 
out  of  the  gauge,  or  the  gauge  away  from  the  work  without 
ruining  the  gauge,  in  case  the  work  should  stick. 

A few  special  cases  of  gauge  making  are  given  below ; the 
gauges  shown  and  the  remarks  made  in  regard  to  them  are 
intended  only  as  suggestions  of  how  a gauge  may  be  made 
for  the  pieces  of  work  shown.  It  is  not  to  be  inferred  that 
the  way  the  gauges  are  made  is,  in  each  instance,  the  best 
method  of  construction  possible  and  the  only  one  applicable. 
Circumstances  alter  cases;  while  a gauge  designed  as  shown 
may  be  eminently  suitable  for  one  set  of  conditions,  it  may 
be  either  too  refined  or  not  refined  enough  for  other  condi- 
tions and  requirements. 


50.  In  Fig.  29  (a)  is  shown  a rather  simple  piece  of 
work,  which  is  finished  on  the  edges  in  a profiling  machine, 


(a) 


and  has  a hole  through  one  end.  The  sides  are  to  be  par- 
allel and  of  a given  thickness.  It  is  required  to  gauge  the 
shape  in  relation  to  the  hole;  it  is  also  essential  that  the  hole 
and  the  thickness  be  correct.  To  gauge  the  hole,  a cylin- 
drical limit  gauge  may  be  employed  ; for  the  thickness,  a 


44 


GAUGES  AND  GAUGE  MAKING. 


28 


limit  snap  gauge  is  best  adapted  ; for  gauging  the  shape,  a 
gauge  may  be  made  as  shownvin  Fig.  29  ( b ).  The  gauge 

consists  essentially  of  a flat  plate  a pierced  by  a hole  of  the 
same  shape  and  size  as  the  work.  This  plate  is  mounted  on 
a block  b,  which  carries  the  pin  c,  and  the  latter  serves  to 
locate  the  work  properly  in  the  gauge.  The  pin  is  made  the 
minimum  size  allowable  for  the  hole  in  the  work.  Then,  if 
the  work  is  placed  over  the  pin  and  if  it  drops  into  the  hole 
pierced  through  it  is  known  that  the  shape  of  the  piece  is 
not  over  the  size. 

The  degree  of  accuracy  with  which  the  work  fits  into  the 
gauge  is  determined  by  ocular  inspection.  While  the  gauge 
shown  determines  whether  the  piece  of  work  will  go  into 
place  or  not  when  the  machine  or  device  that  it  is  intended 
for  is  assembled,  it  does  not  determine  whether  it  is  too 
small  to  satisfactorily  perform  its  allotted  function.  But, 
if  another  gauge  is  made  similar  to  that  shown  in  Fig.  29  (b), 
preferably  on  the  same  block,  and  if  this  second  gauge  is 
made  slightly  below  the  minimum  size  permissible,  a limit 
gauge  would  be  thus  obtained.  In  that  case,  if  the  work 
enters  the  smaller  gauge,  it  is  proved  to  be  too  small ; if 
it  refuses  to  enter  the  larger  gauge,  it  is  shown  to  be  too 
large;  but  if  it  enters  the  large. gauge  and  does  not  enter 
the  small  one,  it  is  correct  in  size  within  the  amount  of 
variation  existing  between  the  large  and  the  small  gauge. 

In  order  that  the  work  may  readily  be  removed  from  the 
gauge,  a large  hole  may  be  drilled  through  the  block  b , 
as  shown  in  the  illustration.  The  work  is  then  pushed  out 
of  the  gauge  either  with  the  fingers  or  with  a small  wooden 
or  metallic  rod. 

51.  A somewhat  different  case  of  gauging  is  shown  in 
Fig.  30.  In  this  instance,  the  object  of  gauging  is  to  deter- 
mine whether  the  center-to-center  distance  a of  the  holes  is 
correct  within  the  predetermined  limit  of  variation.  The 
simplest  kind  of  gauge  for  this  work  is  a plate  with  two  fixed 
gauge  pins  of  correct  diameter  placed  the  required  distance 
apart.  Such  a gauge  is  open  to  one  objection,  however.  If 


§28 


GAUGES  AND  GAUGE  MAKING. 


45 


the  pins  happen  to  fit  the  holes  in  the  work  rather  closely, 
it  is  quite  difficult  to  remove  the  work  from  the  pins  after  it 
has  been  forced  on,  since  it  is  not  an  easy  job  to  draw  the 


Fig.  30. 


work  off  squarely.  This  objection  can  be  overcome  by  ma- 
king one  of  the  pins,  as  b , movable;  it  is  then  to  be  made  a 
good  sliding  fit  in  the  body  of  the  gauge.  The  other  pin, 
as  c,  is  rigidly  fixed.  Withdrawing  the  movable  pin  allows 
the  work  to  be  readily  drawn  off  the  fixed  gauge  pin. 


52.  A pin  gauge  of  the  construction  shown  in  Fig.  30 
apparently  forms  at  the  same  time  a limit  gauge.  Referring 
to  Fig.  31,  let  b and  c be 
the  gauge  pins.  Let  them 
be  placed  1.18  inches 
from  center  to  center. 

Assume  that  the  holes 
in  the  work,  by  pre- 
vious gauging,  have  been 
proved  to  be  larger  than 
.449  and  smaller  than 
.451  inch.  Then,  obvi- 
ously, the  gauge  pins 
must  be  made  small 
enough  to  enter  the  holes 
when  their  size  is  the  smallest  permissible,  i.  e.,  .449  inch. 
Now,  assuming  that  the  holes  are  larger,  say  .451  inch,  the 
work  will  go  over  the  gauge  when  the  side  of  the  holes 


46 


GAUGES  AND  GAUGE  MAKING. 


§28 


touches  the  inside  of  the  gauge  pins,  as  in  Fig.  31  (#),  or  the 
outside  of  the  gauge  pins,  as  in  Fig.  31  (b),  and  also  when 
the  center-to-center  distance,  for  the  size  of  . hole  assumed, 
varies  between  these  two  extreme  positions.  In  the  first 
extreme  position,  the  center-to-center  distance  will  be 
1.182  inches;  in  the  other,  it  will  be  1.178  inches.  We 
thus  obtain  as  the  extreme  limit  of  variation  1.182  inches 
— 1.178  inches  — .004  inch,  or,  as  the  limit  of  variation  in  the 
size  of  the  holes  is  .451  inph  — .449  inch  = .002  inch,  a vari- 
ation double  that  which  is  permitted  in  the  size  of  the  holes. 

Now,  suppose  that  the  holes  in  the  work  happen  to  be  the 
same  size  as  the  gauge  pins.  Then,  the  work  will  not  enter 
at  all  unless  the  center-to-center  distance  of  the  holes  coin- 
cides with  that  of  the  guide  pins.  If  it  varies  but  .001  inch 
from  it,  the  gauge  will  not  go  into  the  holes;  the  work  may 
thus  appear  worthless  when  in  reality  the  holes  may  be 
located  quite  within  the  permissible  limit  of  variation. 

Now,  suppose  that  the  gauge  pins  are  made  smaller  than 
the  smallest  size  of  hole  permissible,  say  .002  inch,  thus 
making  their  diameter  .447  inch.  Then,  if  they  are  placed 
1.18  inches  from  center  to  center,  the  work  will  go  over  the 
pins  if  the  center-to-center  distance  of  the  holes  varies 
between  1.178  and  1.182  inches,  if  the  holes  are  the  smallest 
permissible  size.  If,  however,  they  are  the  largest  size 
allowable,  as  .451  inch,  the  work  will  go  over  the  gauge 
pins  if  the  center-to-center  distance  varies  between  1.176 
and  1.184  inches. 

53.  Having  seen  that  reducing  the  diameter  of  the 
gauge  pins  results  in  an  increase  of  the  range  of  variation 
within  which  the  work  will  pass  over  the  gauge  pins,  we  will 
now  investigate  how  this  range  can  be  reduced. 

The  most  obvious  way  is  to  reduce  the  limit  of  variation 
in  the  size  of  the  holes.  Suppose  that  the  holes  being  nom- 
inally .45  inch  in  diameter,  we  place  their  limiting  sizes  at 
.4495  and  .4505  inch.  If  the  holes  are  small,  say  below 
1 inch,  there  is  not  much  difficulty  in  reaming  them  within 
this  limit.  Then,  if  the  gauge  pins  are  made  .0005  inch 


GAUGES  AND  GAUGE  MAKING. 


47 


§ as 

below  the  smallest  permissible  size  of  hole,  or  .4495  — .0005 
= .449  inch,  the  work  will  go  over  the  pins  if  the  center-to- 
center  distance  of  the  holes  in  the  work  varies  between  the 
limits  of  1.1785  and  1.1815  inches;  that  is,  if  it  varies 
.0015  inch  either  way  from  the  nominal  center-to-center 
distance. 

The  limit  of  variation  in  the  center-to-center  distance  of 
the  holes  that  can  be  detected  by  a pin  gauge  can  be  further 
reduced  by  constructing  one  of  the  pins,  preferably  the  fixed 
pin,  in  such  a manner  that  it  can  be  centrally  expanded  to 
fit  the  hole  in  the  work.  If  this  is  done,  the  limit  of  varia- 
tion in  the  center-to-center  distance  within  which  the  work 
will  go  on  the  gauge  will  be  reduced  to  one-half  of  that 
obtained  otherwise. 

A satisfactory  way  that  may  be  suggested  for  gauging  the 
center-to-center  distance  of  holes  is  to  make  both  pins  adjust- 
able to  the  size  of  the  hole;  one  pin  is  then  rigidly  fixed  and 
the  other  is  mounted  on  a slide  provided  with  a vernier  that 
reads  to  zero  when  the  center-to-center  distance  is  correct. 
If  the  work  is  placed  over  the  pins  and  both  pins  are  then 
expanded  to  fit  the  holes,  the  amount  that  their  center-to- 
center  distance  differs  from  the  nominal  distance  is  then 
read  off  directly  by  the  aid  of  the  vernier.  Such  a gauge  is 
rather  expensive;  the  circumstances  of  each  case  must  deter- 
mine if  the  investment  is  advisable. 


54.  In  Fig.  32  is  shown  a suggestion  for  a gauge  intended 
to  gauge  the  center-to-center  distance  a of  holes  at  a right 


48  GAUGES  AND  GAUGE  MAKING.  § 28 

angle  to  each  other.  At  the  same  time,  it  is  intended  to 
gauge  the  distances  b and  ^ between  the  faces  indicated  and 
the  axes,  or  center  lines,  of  the  holes.  A gauge  pin  d may 
be  made  to  fit  closely  in  the  hole  in  the  left-hand  boss;  this 
pin  is  inserted  at  a right  angle  to  the  surface  e.  The  mov- 
able gauge  pin  f fits  the  hole  in  the  right-hand  boss;  it  is 
placed  with  its  center  line  parallel  to  the  surface  e and  the 
distance  b from  it.  Then,  if  the  work  is  placed  over  the 
gauge  pin  d and  then  held  or  clamped  with  the  clamping  bolt 
shown  against  the  surface  e , while  the  upper  surface  of  the 
right-hand  boss  is  against  the  stop  g,  it  will  be  seen  that 
the  gauge  pin  /cannot  enter  and  pass  through  the  hole  of 
the  right-hand  boss  unless  the  distances  a,  by  and  c are 
correct. 


DIES  AND  DIE  MAKING. 

(PART  1.) 


DIES  AND  PUNCHES. 


GENERAL  FEATURES. 


DEFINITIONS  AND  EXPLANATIONS. 

1.  Meaning  of  the  Term  Die. — Dies  are  devices  for 
cutting,  forming,  or  otherwise  manipulating  metals  and 
other  substances.  They  are  ordinarily  grouped  in  pairs  and 
act  together,  being  moved  toward  one  another,  usually 
under  heavy  pressure.  One  die  alone  could  not  do  the  work ; 
there  must  be  something  to  press  the  material  into  it,  and 
that  something  is  the  other  die,  its  mate.  Such  a pair  of 
tools  is  sometimes  called  a die , but  this  term  lacks  definite-* 
ness  and  mistakes  might  occur  when  designating  one  or  the 
other  tools  in  question.  Although  somewhat  awkward,  the 
term  a pair  of  dies  seems  to  be  the  better  name,  notwith- 
standing that  in  some  instances  three  separate  members,  or 
possibly  four,  may  be  necessary,  as  in  the  case  of  double- 
action and  triple-action  dies. 

Where  one  die  is  smaller  than,  and  enters,  the  other,  as  in 
punching,  cutting,  and  sometimes  in  forming,  the  entering 
part  is  usually  called  the  punch,  and  the  part  into  which  it 
enters  the  die.  Very  often  the  name  plunger  is  applied  to 
the  punch,  while  the  die  is  not  uncommonly  called  the 
matrix.  Where  either  has  some  peculiar  shape  or  some 

§ 29 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


DIES  AND  DIE  MAKING. 


§29 


(h) 

Fig.  h 


(i) 


§29 


DIES  AND  DIE  MAKING. 


3 


special  function  to  perform,  the  workmen  operating  it  may- 
give  it  a special  name,  but  the  names  given  are  now  in 
almost  universal  use. 

2.  The  Ram  and  Bed. — Before  classifying  dies  into 
special  kinds,  it  will  be  well  to  consider  some  features  that 
are  common  to  almost  any  kind,  such,  for  instance,  as  the 
various  methods  of  fastening  the  punch  to  the  ram,  and  the 
die  to  the  bed , of  the  press  in  which  they  are  to  be  operated. 
The  bed  is  the  solid,  or  anvil,  part  of  the  machine,  on 
which  the  die  is  fastened,  while  the  ram  is  the  moving 
member  usually  descending  from  above,  to  which  the  punch 
is  attached.  Occasionally,  however,  the  ram  works  from 
below  and  may  be  so  enlarged  at  the  top  as  to  form  a moving 
bed,  while  the  stationary  part  of  the  press  holds  the  upper 
die  and  is  in  such  case  termed  the  head. 

3.  Methods  of  Fastening  Dies. — In  Fig.  1 is  shown 
a group  of  dies  that  may  be  of  any  of  the  various  kinds,  as 
far  as  the  method  of  attachment  is  concerned.  At  (a)  is 
shown  a punch  a with  a cylindrical  shank  b,  to  be  held  by  a 
setscrew  or  clamp  in  the  ram,  and  a die  c , adjustably  held  in 
a chuck  d by  setscrews  e,  e , the  chuck  having  a flange  f 
that  may  be  gripped  with  clamps  on  the  bed,  or  bolster,  of 
the  press.  A bolster,  in  general,  is  a flat  plate  lying  loose 
upon  the  bed,  so  that  it  may  be  adjusted  laterally  and 
clamped  down  in  any  desired  position.  Its  purpose  is  to 
partly  fill  any  space  where  the  dies  happen  to  be  thin,  and 
also  to  act  as  a bridge  over  any  hole  in  a press  bed,  especially 
when  small  dies  are  to  be  attached. 

At  ( b ) is  shown  a punch  a with  a conical  shank  b , to  be 
held  by  a setscrew  in  the  countersink  c.  The  die  d is  cylin- 
drical and  is  held  in  the  chuck  'e  by  the  setscrew  f,  which  fits 
into  a countersink  similar  to  that  shown  at  c , in  the  punch. 
The  chuck  has  holes  in  its  flange,  through  which  tap-bolts 
may  be  screwed  into  the  bolster. 

At  ( c ) is  shown  a punch  a with  a screw  thread  b that  is  to 
be  screwed  into  the  ram,  and  a die  c screwed  into  the 
chuck  d.  The  flange  of  the  chuck  is  held  by  clamps  to  the 


4 


DIES  AND  DIE  MAKING. 


§29 


bolster.  Both  the  punch  and  die  have  holes  e for  a span- 
ner, with  which  they  are  to  be  turned.  A wedge  fastening  is 
shown  at  (d),  where  both  the  punch  a and  the  die  b are  of  a 
dovetail  section,  the  punch  to  be  held  in  the  ram  and  the  die 
in  the  chuck  by  wedges. 

At  ( e ) is  shown  a punch  a , to  be  held  to  the  ram  by  tap 
bolts  through  the  flange  b,  and  a die  c held  direct  to  the 
bolster,  or  bed,  by  tap  bolts  running  through  the  holes  d , d 
and  screwing  into  the  bolster. 

A pair  of  cutting  dies,  as  shown  at  (f),  may  be  held  in  a 
similar  manner.  No  flange,  however,  is  used  on  the  punch  a , 
but  tap  bolts  from  above  screw  into  the  body  of  the  punch. 

A pair  of  triple-action  dies  is  shown  at  (g)  with  the  shank  a 
of  the  punch  so  made  as  to  be  loosely  held  in  the  press  plun- 
ger by  a special  latch,  while  the  blank  holder  b is  held  to  the 
flange  of  the  ram  by  tap  bolts.  The  die  c is  clamped  to  the 
top  of  the  bolster,  and  the  matrix  below  is  held  in  the  lower 
plate  of  this  special  bolster  by  a dovetail  and  wedge. 

At  (//)  is  shown  a pair  of  double-action  dies  with  punch  a , 
blank  holder  b , and  die  c , all  made  to  screw  into  place. 

A pair  of  coining  dies  are  shown  at  (i)  with  their  collar  a. 
They  are  of  conical  shape  and  are  both  held  by  adjustable 
setscrews  in  a manner  similar  to  that  for  holding  the  chuck 
shown  at  ( a ).  The  collar  is  inserted  in  the  bolster  of  the 
press  and  held  by  a clamping  ring. 

4.  Comparison  of  Fastenings  for  Dies. — Obviously, 
various  other  devices  may  be  used,  the  object  being  merely  to 
fasten  rigidly  one  of  the  dies  so  that  it  cannot  shift  while  at 
work,  the  other  being  adjusted  exactly  under  it  by  trying 
them  together,  and  then  both  being  securely  fastened  to  the 
press.  The  old-fashioned  way  was  to  have  the  adjustment 
with  the  setscrews,  as  shown  at  Fig.  1 {a).  The  pressure  of 
these  setscrews  is  apt  to  spring  or  twist  the  die  out  of  shape, 
especially  if  it  happens  to  be  in  the  form  of  a somewhat  thin 
ring.  The  most  modern  system  of  clamping  a die  down  on 
a flat  surface,  after  it  is  located  in  the  proper  position,  is 
shown  at  (c)  and  (e). 


DIES  AND  DIE  MAKING. 


5 


§29 


It  must  not  be  understood  that  the  various  methods  of 
fastening  the  punch  and  die  are  necessarily  arranged  in  pairs 
in  the  order  given,  as  any  of  the  upper  fastenings  may  be 
combined  with  any  of  the  lower  ones.  Neither  are  lower 
dies  always  held  in  chucks,  but  they  are  often  complete  in 
themselves  with  their  flanges.  There  is  an  economy  in  the  use 
of  chucks  where  the  dies  are  small  and  where  there  are  many 
nearly  of  a size.  In  some  cases  upper  chucks  are  used, 
secured  to  the  ram  by  any  one  of  various  methods.  Small 
dies  or  punches  may  then  be  fastened  in  the  chucks. 

5.  Forms  of  Dies. — In  order  to  gain  a general  idea  of 
the  nature  and  almost  infinite  variety  of  the  forms  con- 
structed by  the  use  of  dies,  one  should  study  the  following 


illustrations,  together  with  the  pressed-metal  forms  that  he 
may  see  every  day.  Thinking  of  and  studying  the  forms, 
with  the  question  of  how  they  can  best  be  produced  con- 
tinually before  him,  will  be  of  great  value.  Some  of  the 


(7.  S.  HI.— $9 


6 


DIES  AND  DIE  MAKING. 


§29 


common  varieties  of  these  tools  are  shown  in  Fig.  2.  A 
shearing  punch  and  die  are  shown  at  {a),  which  is  well 
adapted  for  cutting  off  bar  metal  or  making  short,  straight 
cuts.  The  pair  of  dies  shown  at  (b)  is  for  the  purpose  of 
making  fruit-can  tops,  while  the  combination  square  dies 
shown  at  (c)  would  make  very  good  sardine  cans.  At  (d)  is 
shown  a die  chuck  for  the  purpose  of  holding  the  die  in 
place. 

The  range  of  useful  articles  that  are  made  by  dies  is  very 
great,  and  their  value  is  often  much  greater  than  the  cost  of 
their  production.  Fig.  3 shows  some  of  these  shapes.  A 
piece  of  ornamental  ironwork  for  buildings  is  shown  at  (a). 


The  bicycle  pedal  shown  at  (b)  is  made  up  of  several 
stamped  pieces,  while  the  dish  shown  at  ( c ) is  made  of  a 
single  piece  of  metal.  At  ( d ) is  shown  the  ordinary  reaper 
seat,  which  is  now  used  so  extensively  instead  of  those  that 
have  been  cast.  It  is  made  from  a single  piece  of  metal 


CLASSIFICATION. 

6.  Names  of  tlie  Classes. — Dies  may  be  roughly  clas- 
sified according  to  the  operations  that  are  sometimes  per- 
formed upon  a single  piece  of  metal,  as  cutting , forming, 


DIES  AND  DIE  MAKING. 


7 


§29 

curling , drawing , and  coining.  This  classification  is  wholly 
functional,  and  a variety  of  subclasses  may  be  derived  from 
them,  the  names  of  which  are  also  functional.  Thus,  in  the 
cutting  class,  there  are  chiseling,  shearing,  and  punching 
dies,  the  latter  being  really  shearing  tools  with  the  edge 
extending  all  the  way  around,  instead  of  part  way,  as  with 
shear  blades.  There  are  also  repunching  or  drifting  dies, 
which  are  really  more  in  the  nature  of  the  paring  tools  of  the 
machinist,  the  process  being  somewhat  analogous  to  planing 
or  slotting. 

In  the  forming  class,  besides  forming  dies  proper,  there 
are  bending,  embossing,  and  seaming  dies.  The  seaming 
dies  are  often  in  the  form  of  horn  dies,  where  the  work  is 
placed  upon  a cylindrical  or  prismatic  horn,  and  has  its 
seam  at  the  jointed  side  tightly  mashed. 

The  curling  class  is  generally  used  in  a preliminary 
operation,  or  with  other  dies  in  a series,  and  is  for  the  pur- 
pose of  turning  over  or  curling  edges  and  rims  of  various 
articles. 

In  the  drawing  class  are  the  single-action  and  double- 
action processes,  also  various  forms  of  redrawing,  with  diam- 
eters decreasing  from  the  original  operation.  There  are  also 
analogous  operations,  such  as  wire  drawing  and  spinning, 
which,  not  being  performed  by  presses,  need  hardly  be  fur- 
ther considered  here. 

In  the  coining  class  are  the  analogous  operations  of 
drop  forging  and  squirting.  The  latter  process  is  the  one 
by  which  are  made  the  soft-metal  collapsible  tubes  that  are 
so  largely  used  for  holding  artists’  paints  and  other  semi- 
liquid substances.  Both  this  and  coining,  as  well  as  some 
others,  are  notable  instances  of  the  flow  of  solids. 

Additional  complication  in  the  names  of.  these  tools  are 
caused  by  the  use  of  combination  dies,  which  are  usually 
known  by  this  name,  although  sometimes  called  compound 
dies.  In  general,  they  combine  the  functions  of  cutting 
and  forming,  cutting  and  drawing,  or  cutting  and  emboss- 
ing, as  used  largely  in  the  making  of  shallow  or  deep  tops 
and  lids  for  fruit  cans,  blacking  boxes,  kitchen  utensils,  etc, 


8 


DIES  AND  DIE  MAKING. 


§ 29 


The  term  compound  will  be  used  in  this  Section  for  dies  com- 
bining similar  processes,  as  several  cutting,  or  several  form- 
ing operations. 

A still  further  ambiguity  in  the  naming  of  these  tools 
occurs  with  the  various  kinds  of  gang  dies.  The  adjective 
gang  alone  does  not  mean  anything  very  definite,  but  is 
generally  applied  to  a group  of  punches  and  dies  fastened  in 
common  into  their  respective  plates.  Sometimes  these  are 
all  alike,  as  in  gang-cutting  dies,  where  a large  number  of 
similar  pieces  are  to  be  punched  at  the  same  time.  In  other 
cases  the  pieces  may  be  different,  or  some  of  the  dies  in  the 
gang  may  be  cutting  dies,  and  some  forming  or  embossing 
dies.  Certain  forms  of  gang  dies  are  known  as  progressive 
dies.  These  are  generally  used  for  cutting,  but  sometimes 
for  cutting  and  forming,  at  successive  operations,  on  the  same 
piece  of  material,  as  in  cutting  washers,  cutting  and  emboss- 
ing tobacco  tags,  etc.  For  cutting  an  ordinary  washer, 
for  instance,  a hole  is  punched  at  the  end  of  a strip  of  iron, 
which  is  then  passed  to  a second  position,  where  a pilot  pin, 
projecting  from  the  bottom  of  a larger  punch,  enters  the 
hole  previously  made  and  centers  it.  Meanwhile,  the  punch 
descends  into  its  die  and  cuts  the  exterior  periphery  of  the 
washer  around  the  hole  in  question ; at  the  same  time  the 
punch  which  made  that  hole  is  descending  into  its  die  and 
punching  a new  hole  farther  along  the  strip.  This  in  its  turn 
becomes  the  nucleus,  so  to  speak,  for  the  next  washer,  and 
thus  a complete  article  is  produced  at  each  stroke  of  the 
press  after  the  first  one,  until  the  strip  of  metal  is  exhausted. 
In  general,  care  must  be  taken  not  to  make  the  names  of 
dies  too  positive  without  specifying  what  they  are  to  do. 


QUALITY  AND  DESIGN  OF  DIES. 

7.  Temper  Required. — The  popular  idea  of  a die  is 
that  it  must  be  of  the  best  quality  of  steel,  hardened  to  the 
greatest  degree  that  it  will  stand  .without  crumbling.  This 
is  true  for  cutting  dies  for  thick  and  hard  metals,  for  many 


§29 


DIES  AND  DIE  MAKING. 


9 


kinds  of  embossing  dies  for  doing  fine  work,  and  for  coining 
dies;  for  cutting  soft  metals,  say,  under  inch  thick,  and 
even  tin  plate,  sheet  iron,  and  annealed  low-carbon  steel, 
one  of  the  dies  may  be  left  moderately  soft,  with  an  air 
temper  only.  When  the  edges  of  a soft  die  get  dull  it  may 
be  hammered  cold  and  upset  to  bring  the  cutting  edge  to 
place  again.  After  this  has  been  done,  the  other  die,  which 
meanwhile  has  been  ground  upon  the  face  to  make  it  sharp, 
is  forced  through  or  over  its  mate,  shaving  the  two  dies  to  a 
perfect  fit. 

In  various  forming  dies,  especially  where  the  work  does 
not  have  vertical  edges,  the  working  parts  may  be  of 
untempered  steel,  usually  of  high  carbon,  to  get  greater 
hardness  and  durability.  In  still  other  cases  the  working 
surface  of  forming,  and  especially  of  drawing,  dies  are  made 
of  a good  quality  of  cast  iron.  This  is  especially  true  where 
the  cup-like  shapes,  such  as  household  utensils,  to  be  formed 
or  drawn,  are  of  an  approximately  spherical  or  conical  form, 
and  where  the  exact  diameter  does  not  need  to  be  main- 
tained. In  other  cases,  wrought  iron  or  mild  steel  is  good 
enough  for  working  surfaces,  sometimes  being  case-hard- 
ened. There  is  economy  in  not  heating  any  part  of  a die 
after  it  is  once  brought  to  shape,  either  for  hardening  or 
case-hardening,  for  in  every  hardening  operation  there  is  a 
risk  of  temper  cracking,  and  every  heating  distorts  the 
metal.  Hence,  in  cutting  dies  where  they  must  be  hardened 
and  the  fit  must  be  good  for  thin  metals,  some  grinding 
should  be  done  after  the  hardening.  This  is  easily  done 
with  round  and  elliptical  shapes,  where  the  grinding  can  be 
done  in  the  lathe,  but  with  irregular  shapes  it  is  often  quite 
difficult. 

S-  Degree  of  Accuracy  Required  in  Dies.  — There 
are  many  degrees  of  accuracy  in  tools  of  this  class,  accord- 
ing to  the  quality  of  work  needed.  In  deciding  the  material, 
hardness,  and  general  quality  of  a pair  of  dies,  the  amount 
of  probable  production  must  be  ascertained.  If  but  a small 
number  of  articles  are  to  be  made,  the  cheapest  possible  dies 


10 


DIES  AND  DIE  MAKING 


§29 


that  will  make  them  properly  should  be  selected.  If,  on  the 
other  hand,  large  quantities  are  to  be  produced,  and 
especially  if  they  must  be  very  uniform  in  dimensions,  it  is 
good  economy  to  spend  any  amount  of  time  and  money 
necessary  upon  the  dies  in  order  to  make  them  as  perfect  as 
possible  in  every  detail ; furthermore,  careful  study  should  be 
given  to  make  them  of  composite  design,  so  that  the  parts 
most  liable  to  wear  can  be  cheaply  replaced,  and  thus  avoid 
making  entirely  new  dies.  Sometimes,  to  lessen  the  risk  of 
cracking  and  to  allow  straightening  the  dies,  so-called  com- 
posite steel  bars3.ro,  used;. these  are  soft  iron  for  two-thirds  of 
their  thickness,  while  the  other  one-third  is  steel,  which  is 
welded  on. 

Another  point  to  be  decided  in  the  case  of  cutting  dies  is 
how  closely  they  shall  fit  each  other.  For  thin  metals,  the 
punch  should  enter  the  die  with  a good  sliding  fit.  For 
punching  bar  and  plate  iron,  it  is  customary  to  make  the 
punch  loose  in  the  die  to  an  amount  equal  to  at  least  one- 
sixteenth  the  thickness  of  the  metal.  Dies  made  in  this  way 
are  more  durable  and  require  considerably  less  pressure  than 
when  fitting  each  other  closely.  Indeed,  it  has  been  found 
by  the  well-known  Seller’s  experiments  that  the  least 
resistance  in  punching  occurs  when  the  punch  is  smaller 
than  the  die  by  one-fifth  of  the  thickness  of  the  metal. 
This,  however,  usually  leaves  the  holes  with  too  much 
taper.  In  punching  boiler  iron  and  various  forms  of  bar 
metal  for  ships,  bridges,  buildings,  etc.,  the  amount  of  taper 
allowed  in  the  holes  is  usually  from  inch  to  T6  inch, 
which  does  no  harm  with  holes  that  are  in  any  case  loose 
upon  their  bolts  or  rivets. 

9.  Attachments  Used  on  Dies. — Many  of  the  ordi- 
nary attachments  to  dies,  which  may  or  may  not  be  applied, 
and  which  are  oftener  needed  for  cutting  dies  than  any  others, 
are  various  forms  of  gauges  for  locating  the  work,  and 
strippers  for  preventing  it  from  rising.  In  shearing,  a 
device  termed  a hold-down  is  often  used.  This  is  simply 
an  arm  extending  out  loosely  over  the  top  of  the  bar  or 


29 


DIES  AND  DIE  MAKING. 


11 


plate  to  be  sheared  to  keep  it  from  tipping,  especially  when 
the  shear  blades  are  worn  and  have  dull  edges. 

lO.  Die  Making  in  General. — There  can  be  no  fixed 
and  definite  rules  for  die  making,  as  is  the  case  with  some 
of  the  other  products  of  the  toolmaker.  While  in  some 
cases  each  die  is  simply  a piece  of  steel  of  the  proper  shape, 
in  other  cases  much  careful  designing  is  needed  to  get  the 
best  results  in  economy  and  durability.  The  choice  of 
widely  differing  methods  is  often  open  to  the  die  maker, 
even  in  the  production  of  a single  article. 


CUTTING  DIES. 


PLAIN  DIES. 

11.  The  plain  die  shown  in  Fig.  4 is  made  up  of  four 
distinct  essential  parts,  which  are:  the  hardened  and  tem- 
pered block  a , which  does  the  cutting ; the  stripper  plate  by 


fig.  4. 


which  strips  the  stock  from  the  punch;  the  guide  strip  c , 
which  guides  the  stock;  and  the  gauge  pin  d , which 
gauges  the  location  of  the  holes  punched  in  the  stock.  By 
stock  is  here  meant  the  material  to  be  punched,  which  in 


DIES  AND  DIE  MAKING. 


12 


§29  • 


most  cases  comes  in  long  parallel  strips,  and  is  generally  fed 
by  hand  or  automatically. 

The  punch  consists  of  not  less  than  three  essential  parts, 
which  are:  the  punch  proper  e,  which  does  the  cutting; 
the  collar  ft  which  takes  the  thrust;  and  the  shank^,  by 
means  of  which  the  punch  is  attached  to  the  ram  of  the 
press.  These  three  parts  may  be  one  piece,  as  shown,  or 
they  may  be  separate  pieces  united  by  suitable  means  to 
form  the  punch. 

Dies  like  the  foregoing  may  be  intended  to  pierce  a hole  of 
a given  shape  through  the  material,  in  which  the  punching 
or  wad  is  the  waste  material,  or  scrap,  as  it  is  commonly 
termed,  or  it  may  be  that  the  punching  is  the  article  desired, 
in  which  case  the  remainder  of  the  stock  is  the  scrap. 


12.  Self-Centering  Punch. — Dies  intended  chiefly 
for  producing  holes  do  not  always  need  a gauge  pin  ; in 

many  cases,  the  material  in  which 
the  holes  are  to  be  punched  is  cen- 
ter-punched at  the  point  at  which  the 
hole  is  to  be  located ; the  punch  may 
then  be  provided  with  a small  coni- 
cal point  a,  Fig.  5,  which  enters  the 
center-punch  mark  and  thus  centers 
the  work.  When  holes  are  to  be 
punched  equidistant,  a gauge  pin 
will  in  many  cases  be  found  of  great 
advantage,  inasmuch  as  by  it  the 
laying  out  of  the  holes  on  the  work 
can  be  avoided.  The  conditions  that 
exist  in  each  case  will  readily  deter- 
mine whether  a gauge  pin  can  advan- 
tageously be  used  or  not. 


fig.  5. 


13.  Spiral  Punch.  — Fig.  6 

shows  a punch  the  cutting  edge  a 
of  which  is  made  in  two  or  more  spiral  curves,  instead  of 
being  in  a single  plane,  as  in  the  one  shown  in  Fig.  5.  This 


DIES  AND  DIE  MAKING. 


13 


§ 29 

is  supposed  to  make  it  cut  more  easily,  but  with  a small 
hole  in  thick  metal  the 
effect  cannot  be  very  great. 

The  dip  or  shear  given  to 
large  punches  working  in 
thin  sheets  enables  the  cut- 
ting to  be  performed  pro- 
gressively ; that  is,  one  end 
is  cut  clear  through  before 
the  Other  end  commences  to 
cut.  This  punch  is  very 
cheaply  mounted  by  the 
shank  b and  coupling  c , 
which  can  also  be  used  to 
hold  any  number  of  other 
punches.  It  is  of  a shape 
that  is  cheaply  made  and 
has  in  it  the  least  possible  material.  In  Fig.  6 the  work  is 
shown  at  d and  the  stripper  plate  at  e. 

A piece  already  punched  may  have  other  punching  done 
within  the  space  enclosed  by  its  bounding  edges  by  means 
of  a second  die,  thus  accomplishing  the  required  result  in 
two  separate  operations. 

14.  Gauge  Die. — The  dies  for  the  second  operation 
may  be  arranged  as  shown  in  Fig.  7.  The  punching,  or 
blank,  as  it  is  often  termed,  turned  out  by  the  first  opera- 
tion is  shown  at  (a) ; this  is  to  be  pierced  by  the  holes  a 
and  a\  see  (b).  The  die  is  pierced  with  properly  located 
holes  of  correct  diameter  and  the  punch  plate  is  provided 
with  two  punches,  as  b and  b' . The  sectional  view  of  the 
die  is  taken  on  the  line  A B.  The  guide  strip  and  the 
gauge  pin  of  the  first  operation  die  are  here  replaced  by  a 
gauge  plate  c attached  to  the  die.  This  is  fastened  in 
such  a position  that  it  will  properly  locate  the  blank  in  rela- 
tion to  the  holes  in  the  die. 

The  gauge  plate  has  an  opening  of  the  same  shape  as 
the  blank,  but  sufficiently  larger  to  allow  it  to  be  freely 


Fig.  6. 


14 


DIES  AND  DIE.  MAKING. 


§29 

inserted.  If  a stripper  is  attached  to  the  die,  it  will  not  only 
be  difficult  to  insert  the  blank  in  the  gauge  plate,  but  it  will 
also  be  difficult  to  remove  it.  It  is  also  difficult  to  keep 
clean  the  opening  in  the  gauge  plate.  To  overcome  these 
objections,  the  stripper  d may  be  fitted  to  the  punch,  being 


Fig.  7. 


attached  by  means  of  two  heavy  screws  <?,  which  permit  it 
to  move  upwards.  Heavy  coiled  springs/"  hold  the  stripper 
in  its  lowest  position,  which  is  so  governed  by  the  length  of 
the  screws  that  its  lowest  surface  projects  slightly  beyond 
the  faces  of  the  punches. 

Imagine  the  die  to  be  in  place  and  that  a blank  is  placed 
in  the  opening  of  the  gauge  plate.  Then,  if  the  punch 
descends,  the  stripper  comes  in  contact  with  the  blank  and 
remains  stationary.  As  the  punch  continues  to  descend, 
the  coiled  springs  are  compressed;  the  punches  pass  through 
the  blank,  and  when  they  return,  the  springs,  by  acting 
on  the  stripper,  strip  the  blank  from  the  punches. 


DIES  AND  DIE  MAKING. 


15 


§29 

In  order  that  the  gauge  plate  may  not  shift,  it  is  doweled 
to  the  die  by  means  of  the  dowel-pins  g,g,  and  is  held  down 
by  flat-headed  or  fillister-headed  screws.  To  allow  the  blank 
to  be  readily  removed  from  the  gauge  plate,  a part  of  the 
circumference  of  the  opening  may  be  beveled,  as  shown 
at  h.  A wedge  can  then  be  used  for  prying  out  the  blank. 
For  rapid  work,  it  may  be  advisable  to  devise  some  lever 
arrangement,  operated  by  some  moving  part  of  the  press, 
that  will  automatically  throw  the  blank  out  of  the  gauge 
plate  after  punching.  The  gauge  plate  is  often  made  so 
that  it  encircles  about  one-half  the  blank,  which  is  then 
pushed  against  the  gauge,  and  after  punching  can  be 
removed  by  being  slipped  out.  This  arrangement  is  some- 
what objectionable  on  account  of  the  liability  of  the  blanks 
moving  slightly  away  from  the  gauge  before  the  punch 
strikes  it. 

By  using  a second  die  fitted  with  a gauge  plate  the  holes 
can  be  located  very  closely,  so  that  all  punchings  will  be 
very  nearly  duplicates.  Since,  however,  this  requires  a 
second  operation,  the  time  cost  per  punch  will  be  more  than 
double  what  it  would  be  if  the  blank  and  the  holes  could  be 
produced  in  one  operation. 


PROGRESSIVE  DIES. 

15.  Progressive,  or  gang,  dies  are  intended  to 
remedy  the  defect  of  excessive  time  cost,  but  some  designs 
are  open  to  the  objection  that,  while  they  accomplish  their 
primary  object,  they  cannot  be  relied  on  to  produce  duplicate 
work,  since  they  depend  largely  on  the  straightness  of  the 
stock  and  the  skill  of  the  press  operator  to  produce  good 
work.  A common  design  is  shown  in  Fig.  8,  which  is 
arranged  to  punch  the  same  piece  shown  in  Fig.  7 ( b ).  For 
this  purpose,  the  die  contains  three  holes:  a and  a'  are  for 
punching  the  holes  within  the  blank  and  b for  punching  the 
blank  itself.  The  stripper  is  shown  at  c and  the  gauge  pin 
at  d.  Two  guide  strips  e , e guide  the  stock  between  them. 


16 


DIES  AND  DIE  MAKING. 


29 


When  starting  a strip  of  stock,  it  is  inserted  at  the  left  of 

the  die,  below  the 
stripper,  and 
pushed  forwards 
until  its  end  rests 
against  the  gauge 
pin  at  d.  The 
punch  then  cuts 
out  one  blank  that 
has  no  holes  in  it, 
which  is  thrown 
away;  A and  A' 
at  the  same  time 
punch  the  holes  a 
and  a' . The  stock 
is  then  pushed 
along  until  the 
left-hand  edge  of 
the  large  punched 
hole  in  the  stock 
comes  against  the 
gauge  pin.  The 
holes  a and  a'  in 
the  stock  are  now 
in  their  correct  po- 
sitions above  the 
opening  b in  the 
die;  as  the  punch 
descends,  it  cuts 
out  a finished 
punching  at  b,  and 
at  the  same  time 
cuts  a new  pair  of 
holes  a and  a! 
through  the  stock. 
Now,  assuming 
that  the  die  is  cor- 
rectly laid  out  and  the  gauge  pin  correctly  located,  it  is 


29 


DIES  AND  DIE  MAKING. 


1? 


readily  .seen  that  if  the  operator  fails  to  push  the  stock 
against  the  gauge  pin,  the  holes  will  not  be  correctly  located 
in  the  blank.  Hence,  although  when  in  skilled  hands,  this 
design  of  dies  will  produce  fairly  accurate  work,  it  cannot 
be  relied  on  to  make  exact  duplicate  pieces.  Whether  this 
consideration  is  of  sufficient  moment  to  prevent  its  use  must 
be  decided  upon  the  merits  of  each  case. 

In  the  design,  two  guide  strips  are  placed  the  required 
distance  apart  to  insure  the  stock  being  properly  fed  in ; 
these  can  be  used,  however,  only  when  the  stock  is  uniform 
in  width  and  straight.  When  it  is  not,  only  one  guide  strip 
can  be  used,  and  the  operator  must  always  push  the  stock 
firmly  against  it.  Should  he  fail  to  do  this  every  time,  the 
holes  will  be  improperly  located  in  some  of  the  punchings. 

In  some  cases  one  of  the  guides  has  springs  back  of  it, 
which  hold  it  against  the  stock,  and  so  hold  the  latter 
against  the  other  guide. 

16.  Self-Centering  Dies. — Fig.  9 shows  a design  that 
is  intended  to  overcome,  to  a large  extent,  the  defects  of 
ordinary  progressive  dies.  The  piece  to  be  punched  is 
shown  at  (a).  In  order  that  the  stock  may  be  properly 
centered  in  case  the  operator  should  fail  to  push  it  against 
the  gauge  pin,  the  punch  is  provided  with  a beveled  pilot 
pin  a.  The  upper  cylindrical  part  of  the  pin  is  made 
an  easy  fit  in  the  circular  hole  that  is  already  punched 
in  the  stock  and  is  so  located  on  the  punch  c that  its 
center  line  coincides  with  the  center  of  the  hole  in  the 
punching. 

This  style  of  die  will  produce  duplicate  work  within  quite 
a small  limit  of  variation,  but  the  pin  must  be  a loose  fit  in 
the  hole  within  the  punching,  so  that  the  latter  will  not  stick 
to  the  punch.  The  limit  of  variation  within  which  the  holes 
will  be  located  inside  of  the  punching  is  equal  to  the  dif- 
ference in  the  diameters  of  the  pin  and  the  hole.  The 
design  shown  is  open  to  one  objection,  however.  Should 
the  punch  come  down  when  the  stock  is  not  in  such  a position 
that  the  pin  is  fairly  over  a hole,  the  pin  is  pretty  sure  to  be 


18 


DIES  AND  DIE  MAKING. 


§29 


broken.  But  this  objection,  if  circumstances  permit  it,  may 
be  overcome  by  making  the  pin  movable  in  an  axial  direction 


(a) 


and  providing  a helical  spring  that  will  be  compressed  by 
the  receding  of  the  pin  in  case  it  strikes  solid  stock. 


COMPOUND  DIES. 

17.  The  Construction  of  a Compound  I)ie. — When 

punchings  pierced  by  holes  must  be  exact  duplicates  of  one 
another,  so-called  compound  dies  are  necessary.  These 


§ 29 


DIES  AND  DIE  MAKING. 


19 


Fig.  10. 


20 


DIES  AND  DIE  MAKING. 


§ 29 


differ  from  plain  and  progressive  dies  in  that  both  the  upper 
and  the  lower  die  have  the  punch  and  die  cutter  and  a stripper. 
Compound  dies  do  not  depend  in  any  way  on  the  skill  of  the 
operator,  and  will  make  all  punchings  exactly  alike,  as 
becomes  apparent  when  their  construction  is  studied. 

An  approved  design  for  compound  dies  is  shown  in  Fig.  10. 
At  (a)  is  shown  a vertical  section  and  a plan  view  of  the 
lower  die;  at  (b)  is  shown  a vertical  section  and  a bottom 
view  of  the  upper  die;  while  at  (c)  is  shown  the  complete 
punching,  which  is  produced  in  one  operation.  Referring 
to  (a),  the  tool-steel  block  shown  at  a is  both  a die  and  a 
punch.  It  is  fitted  to  a recess  cut  into  the  plate  b and  is 
attached  to  it  by  means  of  the  screws  shown.  The  block  a 
is  surrounded  by  the  axially  movable  stripper  c,  confined  as 
to  its  uppermost  position  by  the  heads  of  the  screws  d , d , 
which  engage  shoulders  within  the  base.  The  stripper  is 
held  up  by  heavy  helical  springs  e,  e.  The  guide  strip  f and 
gauge  pin  g are  fastened  to  the  stripper. 

The  upper  die  differs  from  the  lower  in  that  the  punch 
block  A and  the  punches  /,  / are  separate,  but  they  are  each 
rigidly  fastened  to  the  plate  B,  which  fits  the  ram  of  the  press. 
The  stripper  D fits  in  the  block  and  surrounds  the  punches; 
it  is  axially  movable,  being  confined  as  to  its  lowest  position 
by  a shoulder  and  held  down  by  helical  springs  A,  which  in 
this  particular  case  surrounds  the  punches.  The  outside  of  a 
in  ( a ) fits  the  inside  of  the  A in  ( b),  and  /,  I fit  the  holes  in  (a). 


18.  The  operation  of  a compound  die  is  as  follows:  The 
stock  having  been  placed  against  the  guide  and  the  gauge 
pin,  the  upper  die  in  descending  first  depresses  the  lower 
stripper  until  the  stock  touches  the  upper  surface  of  a . As 
the  upper  die  continues  to  descend,  it  punches  the  outside 
of  the  punching  and  the  inside  holes  at  the  same  time;  the 
punching  passes  into  the  upper  die,  pushing  the  stripper  D 
upwards.  When  the  upper  die  moves  up  -again,  the  lower 
stripper  c , under  the  influence  of  its  springs,  strips  the  stock 
from  a;  at  the  same  time,  the  upper  stripper  /Rejects  the 
punching  from  the  upper  die.  The  scrap  punched  from 


29 


DIES  AND  DIE  MAKING. 


21 


within  the  punching  discharges  down  through  the  holes  in 
the  lower  die,  which  are  given  clearance  to  facilitate  its 
descent.  No  clearance  is  given  to  the  hole  within  the 
upper  die. 

Compound  dies  by  reason  of  their  construction  will  pro- 
duce the  most  accurate  work,  but  are  quite  expensive  as  far 
as  first  cost  is  concerned ; hence,  if  accuracy  is  not  a par- 
amount consideration,  progressive  dies  may  be  used  advan- 
tageously; but  if  accuracy  is  absolutely  essential,  compound 
dies  should  be  used.  Such  dies  are  largely  used  for  armature 
disks,  and  for  clock  and  watch  wheels.  These  small  dies 
are  usually  mounted  in  subpresses. 


LAYING  OUT  DIES. 

19.  Economy  in  the  Use  of  Stock. — Before  a die  is 
laid  out,  i.  e.,  before  the  outline  of  the  hole  and  the  exact 
location  of  the  gauge  pin  can  be  marked  on  the  surface  of 
the  lower  die,  the  toolmaker  must  determine  which  is  the 
most  economical  way  of  punching  the  stock.  Then,  he  must 
so  lay  out  the  die  that  the  greatest  number  of  punchings 
can  be  obtained  from  a given  weight  of  stock,  in  order  to 
reduce  the  waste  to  the  lowest  figure.  This  is  a matter  that 
requires  a great  deal  of  judgment.  It  has  been  found  to  be 
a good  plan  to  cut  a few  pieces  of  paper  to  the  required  out- 
line of  the  punching;  then,  by  arranging  them  in  different 
ways,  one  is  usually  able  to  determine  quite  rapidly  the  most 
economical  system  of  locating. 

Cases  illustrating  right  and  wrong  ways  of  punching  stock 
are  shown  in  Fig.  11,  where  a represents  the  stock  and  b,  b 
the  holes  remaining  after  the  punching  has  been  done. 
Referring  to  (a),  the  strip  of  stock  is  seen  to  have  passed 
but  once  through  the  press,  leaving  an  enormous  amount  of 
waste.  In  (b)  the  gauge  pin  was  so  located  that  there  was 
sufficient  stock  left  between  each  pair  of  holes,  after  passing 
the  strip  entirely  through  the  press,  to  allow  it  to  be  reversed 
and  passed  through  once  more,  punching  out  most  of  the 

C.  S.  III.— 40 


22 


DIES  AND  DIE  MAKING. 


29 


metal  that  remained  between  the  holes  after  the  first  punch- 
ing. Inspection  shows  that  by  arranging  the  operations  to 


(a) 


Fig.  11. 


take  place  as  in  (b),  a great  many  more  punchings  can  be 
obtained,  and  that,  therefore,  this  method  is  the  more  eco- 
nomical. 

An  appreciable  economy  can  often  be  obtained  by  the 
judicious  selection  of  a proper  width  of  stock.  Thus,  in 


fig.  12. 

Fig.  12,  supposing  a to  represent  the  stock,  and  b the  holes 
left  after  punching,  it  can  be  seen  that  by  using  stock  wide 


DIES  AND  DIE  MAKING. 


23 


§29 

enough  to  punch  staggered  holes,  as  in  (#),  less  material 
will  be  required  for  a given  number  of  punchings  than  is 
needed  when  using  a narrow  strip,  as  in  ( a ).  By  measuring, 
it  will  be  seen  that  the  wide  stock  is  not  twice  as  wide  as  the 
narrow,  although  it  will  practically  give  twice  the  number 
of  punchings  for  equal  lengths  of  strips.  Paper  or  tin-plate 
models  having  the  required  outline  can  also  be  used  advan- 
tageously for  finding  the  best  width  of  stock. 

20.  Position  of  tlie  Gauge  Pin. — The  part  of  the 
gauge  pin  that  forms  the  stop  for  the  stock  determines  by 
its  position  the  amount  of  stock  .that  remains  between  the 
punched  holes.  This  amount  at  the  narrowest  point  between 
adjacent  holes  should,  in  general,  never  be  less  than  the 
thickness  of  the  stock,  and  may  be  slightly  more  for  very 
thin  material.  It  should  not  be  forgotten  that  the  punch, 
in  passing  through  the  stock,  tends  to  draw,  and  actually 
does  draw,  some  of  the  surrounding  material  toward  its 
cutting  edges.  If  there  is  too  little  stock  around  its  per- 
iphery, it  is  liable  to  draw  it  inwards  into  the  die,  which  is 
likely  either  to  jam  or  to  break  the  punch  and  die,  or  to 
make  a ragged  punching. 

21-  Laying  Out  a Simple  Die. — To  layout  the  block 
of  a steel-bar  die,  the  upper  surface  is  finished  smooth  by 
filing  or  grinding,  and  then  coppered  by  using  a solution  of 
of  one  part  of  bluestone  (sulphate  of  copper)  and  ten  parts 
of  water.  Have  the  surface  absolutely  free  from  grease, 
and  cover  it  lightly  with  the  solution.  In  a few  minutes 
this  will  have  dried;  a very  thin  film  of  copper  will  be  found 
deposited  on  the  surface,  and  will  adhere  quite  firmly  to  it. 
The  object  of  coppering  is  to  make  fine  lines  more  plainly 
visible  by  the  contrast  in  color  between  the  steel  and  the 
copper.  The  outline  of  the  hole  is  now  laid  out  by  scribed 
lines  in  the  same  position  in  relation  to  the  guide  strip  that 
it  is  to  occupy  in  relation  to  the  edge  of  the  stock.  A 
center  for  the  gauge  pin  is  then  marked  at  a sufficient  dis- 
tance from  the  outline  of  the  hole  to  leave  ample  support  to 
the  cutting  edges.  The  distance  between  the  opening  and 


24 


DIES  AND  DIE  MAKING. 


§29 


the  gauge  pin  against  which  the  stock  is  pushed  is  readily 
determined  from  the  paper  models  laid  on  the  stock.  Meas- 
ure on  a line  parallel  to  the  edge  of  the  stock  the  distance 
between  corresponding  points  of  the  outline  of  the  two 
nearest  models  that  occupy  the  same  position  in  relation  to 
the  edge;  this  is  the  distance  that  the  end  of  the  gauge  pin 
must  be  from  a point  of  the  opening  in  the  die  that  lies  on 
a line  parallel  to  the  guide  strip  and  passes  through  the 
gauge  pin,  and  on  the  side  of  the  opening  farthest  from  the 
gauge  pin.  This  distance  having  been  marked  on  the  die, 
the  laying-out  process  is  complete. 

22.  Laying  Out  Progressive  Dies. — The  holes  first 
punched,  which  are  to  be  located  afterwards  within  the  out- 
line of  the  punching,  must  be  in  such  a relation  to  the  guide 
strip  and  the  gauge  pin  that  they  will  occupy  their  correct 
positions  when  the  stock  is  against  the  end  of  the  gauge  pin. 
This  is  not  a very  difficult  matter. 

Let  A,  B , and  C,  Fig.  13  ( a ),  be  paper  models  of  given 
outline  that  have  been  pasted  on  a piece  of  stock  in  the 
position  in  which  it  is  believed  the  most  economical  use  can 
be  made  of  it.  Then,  parallel  to  the  edge  of  the  stock,  draw 
any  line,  as  a a! , through  the  models.  The  distance  between 
corresponding  points  of  intersection  on  models  occupying 
the  same  relative  positions,  as  between  c and  d,  is  the  dis- 
tance that  any  corresponding  points  must  be  apart  on  the 
die.  When  the  outline  of  the  hole  within  the  punching  is 
circular,  the  die  may  be  laid  out  on  the  surface  of  the  lower 
die  by  laying  out  the  outline  of  the  punching  in  the  same 
position  in  relation  to  the  guide  strip  that  the  model  occu- 
pies in  relation  to  the  edge  of  the  stock.  If  a model  is 
given,  this  may  be  laid  on  the  surface  and  the  outline  trans- 
ferred by  scribing  around  it.  Also  scribe  through  the  hole 
within  the  model,  and  then,  on  the  surface  of  the  die,  mark 
its  center  by  a fine  center-punch  mark.  If  no  model  has 
been  given,  the  outline  and  positions  of  the  holes  within  the 
punching  must  be  transferred  from  the  drawing.  Next, 
through  the  center-punch  mark  just  made,  as  c' , Fig.  13  ($), 


§29 


DIES  AND  DIE  MAKING. 


25 


draw  a straight  line  e f parallel  to  the  guide  strip.  On  this 
line  lay  off  the  distance  c'  cT  equal  to  c d;  the  point  cT  will 
then  be  the  center  of  the  hole.  By  extending  this  method 
of  laying  out,  the  correct  location  of  any  point  on  the  end 
of  the  gauge  pin  maybe  determined.  If  possible,  the  gauge 
pin  should  be  so  located  that  the  act  of  pushing  the  stock 
against  it  will  also  force  it  against  the  guide  strip.  Suppose 
that  it  has  been  decided  to  locate  the  gauge  pin  within  the 


space  included  by  the  lines  a a1  and  bb'\  then  draw  the 
lines  aa\gg\  and  b b'  parallel  to  the  guide  strip.  From 
the  points  where  these  lines  intersect  the  outline,  and  far- 
thest from  the  proposed  location  of  the  gauge  pin,  as  h,  i , 
and  k , set  off  on  them  the  distances  h h\  ii' , and  kk'  equal 
to  c d.  The  points  h\  i\  and  k'  are  then  points  on  the  face 
of  the  gauge  pin.  It  is  not  necessary  to  draw  just  three 
lines  for  this  purpose;  any  convenient  number,  from  one  up, 
may  be  used. 


2G 


DIES  AND  DIE  MAKING. 


§ 29 


23.  A mechanical  way  of  laying  out  the  holes  of  a pro- 
gressive die  involves  the  use  of  a model  and  a templet. 
Both  of  these  may  be  made  advantageously  of  a piece  of 
medium  heavy  tin  plate;  if  this  is  not  available,  thin  sheet 
steel  or  sheet  brass  may  be  used.  Sheet  zinc  is  still  better, 
for  if  deep  scribe  lines  are  scratched  in  it  the  metal  may  be 
broken  like  glass  after  the  diamond.  By  doing  this,  much 
filing  may  be  saved. 

Cut  off  a strip  of  the  same  width  as  the  stock  and  cut  a 
hole  in  it  to.  exactly  fit  the  outline  of  the  model  that  has 
previously  been  made.  Cut  the  hole  in  the  same  position 
relative  to  one  edge  that  the  punched  holes  are  to  occupy 


Fig.  14. 

relative  to  the  edge  of  the  stock.  On  this  templet,  in  any 
convenient  place  on  the  edge,  make  a mark,  as  shown  at  a , 
Fig.  14  (a) ; then,  to  the  right  and  left  of  it,  lay  off  the  dis- 
tances ab  and  ac  equal  to  c d,  Fig.  13  (a).  Now  place  the 
templet  on  the  surface  of  the  die  and  against  the  guide; 


DIES  AND  DIE  MAKING. 


27 


§ 29 

shift  it  to  where  it  has  been  determined  to  place  the  largest 
opening,  and,  after  clamping  it,  scribe  through  the  opening. 
Make  a mark,  as  /,  on  the  surface  of  the  die  in  line  with  the 
mark  a on  the  templet.  Shift  the  templet  along  the  guide 
strip  until  mark  b coincides  with  / and  scribe  through 
again.  This  scribed  outline  gives  the  location  of  the  edge 
of  the  gauge  pin.  Next  insert  the  model  into  the  opening 
of  the  templet  and  shift  it  along  the  guide  strip  until  mark  c 
on  it  is  in  line  with  mark  /.  Now  scribe  through  the  holes 
in  the"  model.  The  laying  out  is  thus  completed.  It  is  a 
good  idea  to  lay  out  the  die  on  a piece  of  paper  first;  this 
will  greatly  aid  in  locating  the  openings  centrally  in  the  die. 

24.  Laying  Out  a Compound  Die. — As  far  as  the 

laying  out  of  a compound  die  is  concerned,  there  are  no 
special  directions  needed.  Probably  the  best  practice  is  to 
make  the  lower  die  first ; the  gauge  pin  may  be  located  on 
the  stripper  in  exactly  the  same  manner  as  with  a plain  die. 


MAKING  THE  DIE. 

25.  Cutting  the  Openings  in  the  Die.  — The 

required  outlines  of  the  openings  having  been  scribed  on 


Fig.  15. 

the  die,  they  may  be  cut  through  by  drilling  a series  of  small 
holes  close  together,  as  shown  in  Fig.  15  (a),  and  then  cut- 
ting out  the  metal  between  the  holes  with  a narrow  drift. 
The  die  is  usually  finished  by  filing  to  the  scribed  lines, 


28 


DIES  AND  DIE  MAKING. 


§29 


making  the  openings  larger  at  the  bottom,  so  that  the  punch- 
ings  may  drop  out  easily.  The  clearance  given  may  be 
from  1°  to  2°;  to  determine  if  the  clearance  .is  the  same  all 
around,  the  die  maker  frequently  uses  a die  maker’s  square, 
which  differs  from  the  try  square  in  that  its  blade,  instead 
of  making  an  angle  of  90°  with  the  stock,  makes  an  angle  of 
90°  plus  the  clearance  angle.  Obviously  the  blade  of  the 
square  must  be  very  narrow  in  order  that  it  may  be  used  for 
small  openings. 

When  cutting  the  openings  in  the  die,  the  toolmaker  can 
often  save  himself  considerable  work,  and  make  a better  job 
at  the  same  time,  by  forming  circular  arcs  by  drilling,  coun- 
terboring, or  reaming,  if  their  formation  by  such  means  is 
possible.  Referring  again  to  Fig.  15,  instead  of  drilling  a 
series  of  small  holes,  two  large  holes  may  be  drilled,  as  shown 
at  (l?),  and  clearance  may  then  be  given  by  reaming  from 
the  bottom  with  a taper  reamer;  considerable  filing  is  thus 
saved,  and,  at  the  same  time,  the  circular  arcs  at  the  two 
ends  of  the  opening  will  be  more  nearly  circular  than  filing 
could  make  them.  The  metal  remaining  between  the  two 
large  holes  can  be  cut  out  by  drilling  the  small  holes  shown, 
and  the  die  can  be  finished  by  filing  the  two  reversed  arcs  to 
the  scribed  lines. 

26.  Filing  Templet  for  Symmetrical  Work. — Dies 

for  work  that  has  an  axis  of  symmetry,  as  a b , Fig.  16  (a), 
can  often  be  made  advantageously  by  the  aid  of  a hardened- 
steel  filing,  or  profiling,  templet,  or  filing  jig , as  it  is 
sometimes  called.  Such  a templet  is  shown  in  plan  view 
at  ( b ).  Thin  tool  steel  about  inch  thick  is  very  good 
material  from  which  to  make  this  templet.  Scribe  a 
straight  line  a ' b'  on  the  templet,  to  represent  the  axis  of 
symmetry.  Then  to  one  side  of  it  lay  out  one  half  of  the 
required  outline,  as  c de  f.  On  the  other  side  lay  out  lines, 
as  c gf,  sufficiently  removed  from  the  axis  of  symmetry  to 
clear  the  other  half  of  the  outline.  Next,  on  lines  perpen- 
dicular to  a'  b\  mark  the  centers  of  the  holes  h , h equidis- 
tant from  a ' b' . These  holes  receive  screws  by  means  of 


§ 29 


DIES  AND  DIE  MAKING. 


29 


which  the  templet  is  to  be  attached  to  the  die.  Drill  two 
small  dowel-pin  holes,  as  i,  i\  so  that  their  centers  lie 
on  a'  b' . Drill  the  holes  h,  h\  cut  out  the  opening  in  the 
templet,  filing  very  carefully  to  the  line  cdef,  and  then 
harden  it.  If  the  templet  is  hardened  in  water  or  oil,  it  will 
be  sprung  considerably;  but  if  after  being  heated  it  is 
quickly  placed  between  two  planed  cast-iron  blocks,  it  will 
remain  almost  flat.  Now  lay  the  templet  on  the  die  and 
clamp  them  together.  Using  the  templet  as  a jig,  drill  the 
dowel-pin  holes,  spot  the  location  of  the  holding-down 


screws,  and  drill  and  tap  holes  to  receive  them.  If  circum- 
stances permit,  it  is  well  to  locate  the  holes  //,  h so  that  they 
can  be  used  afterwards  for  attaching  the  guide  strips  to  the 
die.  Fit  dowel-pins  to  the  holes  drilled  for  them,  and  place 
the  templet  over  them.  Mark  one  half  of  the  outline  on  the 
die  by  scribing  from  the  templet;  then  turn  over  the  templet 
and  scribe  the  other  half.  Rough  out  the  opening  in  the 
die  and  attach  the  templet  to  it  by  means  of  the  screws. 
One  half  of  the  outline  can  now  be  filed  to  the  templet, 
which  is  then  reversed  as  shown  at  (c),  and  the  other  half 
finished.  Obviously,  both  halves  of  the  outline  will  be 
exactly  alike. 


30 


DIES  AND  DIE  MAKING. 


§29 

27.  Giving  Clearance. — Clearance  may  be  given  to 
dies  in  several  ways.  If  the  opening  is  rather  small,  it  can 
usually  be  done  only  by  filing;  when  the  opening  is  large,  a 
tapering  milling  cutter  of  small  diameter  can  often  be  used 
to  advantage  to  rough  out  the  hole.  In  some  cases,  the  die 
may  be  strapped  to  an  angle  plate  that  is  inclined  to  the 
right  angle;  it  may  then  be  roughed  out  by  planing  or  shap- 
ing with  a single-pointed  tool.  It  will  be  necessary  to  finish 
by  filing.  As  a general  rule,  the  clearance  should  not  extend 
directly  to  the  cutting  edge,  but  only  within  about  inch  of 
it.  Then  the  sides  of  the  opening  down  to  the  beginning 
of  the  clearance  should  be  straight,  and  make  an  angle  of  90° 
with  the  bottom  surface  of  the  die.  The  objection  to  carry- 
ing the  clearance  clear  up  to  the  cutting  edge  is  that  any 
sharpening  of  the  die  will  enlarge  the  size  of  the  opening. 

28.  Hardening  and  Tempering  the  Die. — Prior  to 
heating  the  die,  all  holes  that  are  not  intended  for  the  cut- 
ting operation,  such  as  the  gauge-pin  hole  and  the  screw 
holes  for  the  guide  strips,  should  be  plugged.  Fireclay  or 
asbestos  may  be  used  for  plugging.  Heat  the  die  very  slowly 
and  evenly  in  a clear  fire  and  quench  it,  keeping  it  under 
the  quenching  fluid  until  perfectly  cold.  A strong  salt  brine 
is  considered  by  many  to  be  the  best  quenching  fluid,  since 
with  it  the  die  can  be  hardened  satisfactorily  at  a low  heat. 
This  brine  can  be  made  by  placing  in  water  as  much  ordi- 
nary salt  as  the  water  will  dissolve.  If  the  die  is  hardened 
at  a low  heat,  experience  has  shown  that  not  only  is  there 
much  less  danger  of  cracking,  but  also  that  there  is  a great 
reduction  of  the  warping.  In  general  it  will  prove  advisable 
to  harden  at  as  low  heat  as  possible  with  the  grade  of  steel 
used,  no  matter  what  quenching  fluid  is  used.  Experience 
has  shown  that  the  hardening  of  steel  depends  primarily  on 
the  rapidity  with  which  the  heat  is  abstracted  from  it,  and, 
to  a much  smaller  extent,  on  the  temperature  range  through 
which  it  cooled.  Hence  it  follows  that  by  using  brine  the 
same  degree  of  hardness  may  be  obtained  from  a lower 
quenching  heat. 


§ 29 


DIES  AND  DIE  MAKING. 


31 


29.  The  d ie  having  been  hardened,  brighten  its  upper 
surface  and  temper  it  evenly.  A good  way  of  drawing  the 
temper  is  to  place  a rather  heavy  iron  plate,  say,  from  -J- 
to  1 inch  thick,  on  the  fire  and  then  place  the  die  bottom 
side  down  on  it.  Move  it  around  constantly  on  this  hot 
plate,  so  as  to  avoid  local  heating.  The  color  to  which  the 
die  should  be  drawn  depends  largely  on  the  nature  of  the 
material  that  is  to  be  punched  and  on  the  degree  of  hard- 
ness that  was  obtained  in  hardening.  Generally  speaking, 
dies  intended  for  very  thin  and  easily  severed  material  can 
be  left  harder  than  those  intended  for  severe  duty.  The 
average  color  to  which  a die  is  drawn  is  a deep  straw;  how- 
ever, practical  experience  alone  can  determine  if  this  is  the 
proper  color  to  give  in  order  that  the  die  may  last  well. 

After  tempering,  grind  the  bottom  side  of  the  die  to  a 
plane  surface;  a surface  grinder  or  grinding  lathe  is  a suit- 
able machine.  Sharpen  the  cutting  edge  by  grinding  the  top 
surface  and  try  the  model  in  the  opening.  If  this  has  closed 
in  somewhat,  bring  it  to  the  right  size  again  by  oilstoning. 
The  die  is  now  completed  by  putting  in  the  gauge  pin. 

30.  Fitting  the  Punch. — In  American  practice,  the 
punch  is  almost  invariably  made  after  the  die  has  been  com- 
pleted. The  rough  block  is  faced  square  and  flat  on  its 
lower  surface,  which  is  then  coppered.  The  outline  of  the 
opening  in  the  die  is  now  transferred  to  the  punch  block  by 
scribing,  and  it  is  roughed  out  nearly  to  the  line  by  milling, 
planing,  or  even  by  chipping  and  filling.  The  very  end  of 
the  block  is  now  carefully  tapered,  using  the  scribed  outline 
as  a guide  until  it  will  just  enter  into  the  die.  The  punch 
being  made  is  then  pressed  in  slightly,  preferably  in  a press, 
just  enough  to  make  a distinct  witness  mark  showing  where 
metal  is  to  be  removed.  This  is  repeated  until  the  punch 
fits  throughout  its  entire  length.  It  is  then  faced  off  slightly 
on  its  lower  surface  in  order  to  get  rid  of  all  traces  of  the  orig- 
inal beveling,  and  is  ready  for  hardening,  When  fitting  a 
punch  for  gang  dies,  it  is  advisable  to  first  fiGthe  punches  for 
the  largest  opening,  and  then  the  small  ones. 


32 


DIES  AND  DIE  MAKING. 


§ 29 

31.  Hardening;  and  Tempering  the  Punch. — The 

hardening  is  usually  done  in  brine,  using  a clear  fire  for  heat- 
ing. In  case  the  punch  is  made  in  one  piece,  only  the  end 
is  hardened;  it  is  then  drawn  to  the  right  color.  As  in  the 
case  of  the  die,  experience  alone  can  determine  which  is  the 
best  color;  generally  speaking,  the  punch  is  claimed  to  last 
better  if  made  slightly  softer  than  the  die.  Thus,  if  the  die 
has  been  drawn  to  a deep  straw  color,  the  punch  may  be 
drawn  to  a purple  or  even  to  a blue.  After  drawing  the  tem- 
per, try  the  punch  in  the  die;  if  it  is  found  to  have  swollen  in 
hardening,  bring  it  to  size  again  by  grinding  or  oilstoning. 

While  directions  have  been  given  here  for  hardening  and 
tempering  dies,  it  must  not  be  inferred  that  all  cutting  dies 
must  be  hardened.  In  many  cases,  the  extra  expense  of 
hardening  is  not  warranted,  as,  for  instance,  when  only  a 
relatively  small  number  of  punchings  for  soft  material  is 
required.  In  that  case,  both  the  die  and  the  punch  may  be 
left  soft.  Judgment  must  be  used  in  determining  whether 
to  harden  a die  or  not;  if  the  material  is  of  such  a nature 
that  it  will  rapidly  wear  out  the  cutting  edges,  hardening 
may  be  necessary  even  for  a small  number  of  punchings. 

32.  The  Shear  or  Dip  of  Dies. — When  the  face  of  a 
die  is  so  formed  that  one  part  of  the  edge  commences  to  cut 
in  advance  of  other  parts,  it  is  said  to  have  shear.  The 
word  shear  is  in  very  common  use  in  the  sense  just  employed. 
It  is,  however,  used  in  other  slightly  different  senses,  so  that 
in  shops  the  term  dip  is  used  as  a synonym. 

Dies  and  occasionally  punches  may  have  their  cutting 
edges  so  formed  that  the  punching  is  cut  from  the  stock  by 
a shearing  cut.  The  die  is  then  said  to  have  shear.  The 
object  of  giving  shear  is  most  commonly  the  reduction  in  the 
force  required  to  do  the  punching;  in  other  words,  it  allows 
a press  of  a given  capacity  to  punch  work  for  which  ordi- 
narily it  would  not  be  powerful  enough.  Shear  may  be  given 
either  to  the  die  or  to  the  punch,  or  even  to  both. 

A common  way  of  giving  shear  to  the  die  is  shown  in 
Fig.  17,  which  is  a vertical  section.  In  this  case,  the  punch 


29 


DIES  AND  DIE  MAKING. 


33 


is  flat  at  its  cutting  end.  In  coming  down  on  the  stock,  cut- 
ting will  evidently  commence  at  a and  proceed  toward  b and  c 
at  the  same  time.  If  the  punch  is  given  a shear  the  reverse 


Fig.  17. 


of  that  on  the  die,  the  shear  will  be  doubled.  Dies  intended 
to  have  shear  are  usually  made  with  a raised  boss  around  the 
opening,  as  shown  in  the  illustration.  This  makes  them 
easier  to  sharpen. 


Fig.  18. 

33.  Sometimes  the  effect  of  shear  may  be  obtained  in 
other  ways.  Thus,  referring  to  Fig.  18,  where  several  holes 


34 


DIES  AND  DIE  MAKING. 


§29 


are  to  be  punched  in  one  operation,  each  punch  may  be  made 
longer  than  the  one  next  to  it  on  the  left.  Then,  if  their 
difference  in  length  is  made  slightly  more  than  the  thickness 
of  the  stock  to  be  punched,  the  right-hand  punch  will  have 
completely  passed  through  the  stock  before  the  middle  one 
comes  down  on  it,  thus  leaving  the  full  power  of  the  press 
available  for  each  punching  blow. 

34.  When  the  effect  of  shear  is  obtained  as  in  Fig.  18, 
neither  the  work  nor  the  stock  will  be  bent;  if  the  shear  is 
obtained  as  in  Fig.  rL  the  stock  that  is  being  punched  will 
come  out  bent,  but  the  punching  will  remain  almost  flat.  If 
the  shear  is  given  to  the  punch  and  the  die  is  left  flat,  the 
punching  will  come  out  crooked,  but  the  stock  will  be  left 
flat.  If  both  punch  and  die  block  are  given  shear,  usually 
both  the  stock  and  the  punching  will  come  out  crooked. 
From  these  considerations,  the  toolmaker  must  determine 
the  construction  for  each  particular  case. 


DIES  AND  DIE  MAKING. 

(PART  2.) 


DIES  AND  PUNCHES. 


THE  DIFFERENT  FORMING  OPERATIONS. 

1.  Meaning  of  tlie  Term  Forming. — In  a general 
sense,  forming  applies  to  all  operations  with  dies  except  the 
cutting  or  punching  operations.  All  metals  when  in  a state 
susceptible  to  cutting  operations  are  also  more  or  less  sus- 
ceptible to  forming  operations  of  various  kinds.  The  degree 
to  which  they  are  thus  susceptible  depends  chiefly  on  their 
ductility.  There  is  also  a number  of  non-metallic  substances 
on  which  forming  operations  can  be  performed  to  a greater 
or  less  degree,  such  as  paper,  cloth,  leather,  hard  fiber,  wood, 
etc.  Some  of  these  substances  must  be  especially  treated  to 
prepare  them  for  die  working,  as  by  heating,  dampening,  etc. 
The  process  of  forming  in  this  general  sense  really  consists 
chiefly  of  bending  the  material  at  various  points  without 
much  distortion  of  its  area  in  any  particular  localities. 

2.  Forming  and  Bending. — Forming,  in  its  more 
restricted  and  technical  sense,  usually  carries  the  line  in 
which  the  sheet  is  bent  around  in  a circle  or  some  other  con- 
tinuous contour.  Thus,  a flange  or  edge  that  is  bent  at  a 
right  angle,  or  some  other  lesser  angle,  from  the  general 
plane  of  a circular  sheet,  such  as  a tin-can  lid,  has  its 
particles  slightly  disturbed  in  the  way  of  compressing  and 
stretching.  This  action  when  carried  to  a considerable 
extent,  where  much  depth  is  required,  comes  within  the 

§ 30 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


DIES  AND  DIE  MAKING. 


§30 

domains  of  the  drawing  process.  For  shallow  work,  where 
the  depth  is  not  more  than  about  ten  times  the  thickness  of 
the  metal,  and  one-tenth  the  diameter  of  the  work,  single- 
action dies  can  usually  be  employed. 

Bending  proper,  in  a technical  sense,  is  applied  to  cases 
where  the  line  of  change  from  the  general  plane  of  the  metal 
is  a straight  one.  There  is  no  distortion  of  the  particles  other 
than  that  due  to  the  slight  stretch  on  the  outside  and  com- 
pressing on  the  inside  along  the  actual  corner  that  is  bent. 

Bo  Embossing. — Embossing  is  usually  a process  where 
small  areas  of  the  sheet  of  material  are  locally  formed  and 
bent  so  as  to  raise  or  lower  them  from  the  general  plane  of 
the  sheet,  as  in  stamping  letters,  pictures,  and  various  orna- 
mental designs.  In  this  case  there  is  local  stretching  and 
compressing  in  various  spots,  depending  on  the  depth  and 
width  of  the  design.  In  many  cases  only  the  toughest  metals 
will  stand  the  depth  of  relief  required  to  get  the  proper 
cameo  or  intaglio  effect.  In  many  cases  ornamental  designs 
must  be  toned  down,  so  to  speak,  or  made  with  less  relief,  to 
prevent  the  tearing  of  the  metal  in  certain  spots  or  the  undue 
wrinkling  of  it  in  other  places.  Embossing  differs  from  coin- 
ing, as  the  sheet  metal  does  not  change  its  thickness,  but 
is  made  hollow  on  one  side  to  match  every  hump  on  the  other. 


DIES  FOR  FORMING. 

4.  A Simple  Forming  Die. — One  of  the  simplest  and 

most  common  examples 
of  forming  is  illustrated 
in  the  changing  of  the 
flat  circular  blank,  as 
shown  in  Fig.  1 (a),  into 
a cup,  as  shown  at  ( b ). 
This  can  readily  be  done 
in  an  ordinary  single- 
(a)  (b)  action  press  by  the  aid  of 

FlG-  forming  dies.  A sin- 

gle-action press  is  here  defined  as  one  that  has  but  one  ram. 


§30 


DIES  AND  DIE  MAKING. 


3 


The  forming  dies  may  be  constructed  as  shown  in  Fig.  2, 
in  which  a chuck  is  shown  at  a,  which  is  to  be  bolted  to  the 
bed  of  the  press.  The  die,  which  is  shown  at  b , bored  out  to 
the  outside  diameter  of  the  cup  and  polished  on  the  inside, 
is  fastened  to  the  chuck  in  some  convenient  manner.  One 
way  of  doing  this  is  to  attach  it  by  means  of  a gauge 
ring,  as  shown  at  c.  This  ring  is  bored  out  centrally  to  the 
size  of  the  blank,  and  its  correct  position  in  reference  to  the 
die  is  insured  by  fitting  it  to  a raised  cylindrical  projection. 


Fig.  2. 


Two  or  more  holes  may  be  drilled  near  the  circumference  of 
the  gauge  ring,  to  receive  the  pins  of  a spanner  wrench. 
The  punch  d is  made  equal  in  diameter  to  the  inside  diameter 
of  the  cup  to  be  formed.  The  inside  ’ diameter  of  the  cup 
equals  the  outside  diameter  less  twice  the  thickness  of  the 
material.  The  blank  is  inserted  in  the  gauge  ring  of  the 
die,  so  that  the  punch  as  it  descends  bends  up  an  outer  zone 
of  the  blank,  and  in  passing  through  the  die  straightens  out 
the  wrinkles  that  form.  The  punch,  with  the  work  on  its 
C.  5.  III.— 41 


4 


DIES  AND  DIE  MAKING. 


30 


lower  end,  passes  completely  through  the  die.  The  upturned 
edges  of  the  work  spring  slightly  away  from  the  punch,  and 
as  it  ascends  again,  the  edges  catch  against  the  sharp  lower 
edge  of  the  die.  The  work  is  thus  stripped  off  the  punch 
and  falls  through  the  opening  in  the  bed  of  the  press.  The 
upper  inner  edge  of  the  die  must  be  rounded  to  a radius 
of  about  | inch. 

The  die  here  shown  performs  but  one  operation,  which  is 
the  forming  of  the  blank  into  the  required  shape.  It  is 
sometimes  known  as  a plain  forming  die.  Such  dies  may  also 
be  used  for  forming  shallow  hollow  articles  with  a flat  bottom 
and  tapering  or  curved  sides,  such  as  pie  tins  and  similar 
work.  Then  the  lower  die  is  solid,  but  may  be  fitted  with  a 
spring-actuated  ejector,  in  case  the  form  of  the  work  is  such 
that  it  cannot  readily  be  lifted  from  the  die  after  the  form- 
ing operation  has  been  completed. 

5.  Forming  Dies  for  Can  Tops  and  Caps. — The 

tops  of  ordinary  fruit  cans  are  formed  as  shown  at  Fig.  3 (a). 


(b) 

Fig.  3. 


The  bottoms  are  just  like  the  tops,  except  that  the  hole  c 
and  the  beading  d are  omitted,  the  bottoms  being  plain. 
The  edges  of  both  tops  and  bottoms  are  turned  down, 
as  shown  at  e , and  a beading  raised  around  the  edge,  as 
shown  at  f.  In  order  to  accomplish  this,  a combination  die , 
such  as  shown  in  Fig.  3 (£),  is  frequently  used.  This  die 


§30 


DIES  AND  DIE  MAKING 


5 


may  be  arranged  to  cut  either  tops  or  bottoms.  When  it  is 
desired  to  cut  tops,  a small  punch  for  punching  the  holes  c is 
located  at  the  center  of  the  large  punch  b.  The  small  lead 
punch  then  makes  the  hole  c,  forcing  the  waste  stock  through 
the  opening  g in  the  die.  The  outer  edge  of  the  punch  b 
shears  or  punches  the  outer  edge  of  the  can  top  or  bottom, 
the  shearing  taking  place  between  the  edges  of  the  punch  b 
and  the  portion  a of  the  die.  The  lower  face  of  the  punch  b 
is  so  formed  that  it  serves  as  a forming  or  embossing  die  to 
turn  down  the  edges  c , raise  the  ridge  fy  and  form  the 
depression  d in  the  can  top.  The  portion  for  forming  the 
depression  d is  placed  on  the  same  piece  that  carries 
the  punch  for  punching  the  hole  c,  and  this  piece  is  arranged 
to  screw  into  the  center  of  the  die.  The  loose  piece  is 
shown  at  Fig  3.  (r),  the  cutting  edge  that  cuts  out  the  hole  c 
in  the  top  being  shown  at  //,  and  the  ridge  that  draws  the 
depression  d being  shown  at  i.  The  flat  surface  j corresponds 
to  the  flat  surface  k in  the  top  When  it  is  desired  to 
punch  can  bottoms,  the  piece  shown  at  Fig.  3 (c)  is 
unscrewed  from  the  punch  b,  and  the  center  of  the  bottom 
will  remain  flat. 

In  order  to  form  the  small  caps  that  cover  the  opening  c, 
a punch  of  the  form  shown  in  Fig.  4 is  frequently  used.  The 
general  form  of  the  cap  is 
shown  at  a,  and  it  will  be 
noticed  that  its  outer  edges 
are  turned  down  and  that 
in  the  center  there  is  a 
small  hole  to  serve  as  a vent 
hole  when  the  can  is  being 
sealed.  The  outer  edge  of 
the  cap  is  cut  by  a punch  b , 
the  central  portion  of  the 
die  c being  arranged  on 
springs,  so  that  it  descends 
a certain  distance  in  contact  with  the  stock,  which  is  held 
between  the  die  and  the  punch,  the  cutting  being  done 
between  the  punch  b and  the  die  d , while  the  forming  is 


fig.  4. 


6 


DIES  AND  DIE  MAKING. 


30 


done  between  the  punch  b and  the  die  c.  ' The  small  hole  at 
the  center  of  the  cap  is  formed  by  a small  punch  located 
at  the  center  of  b,  which  enters  the  hole  e. 

These  two  sets  of  punches  and  dies  are  illustrated  to  show 
some  of  the  classes  of  work  that  can  be  made  with  this  style 
of  tool.  Many  pieces  of  metal  of  complicated  form  can  be 
made  by  combination  punches  and  dies  by  properly  arran- 
ging the  cutting  and  forming  portions  of  the  dies.  The  solu- 
tion of  any  problem  of  this  kind  is  simply  an  application  of 
the  principles  illustrated  in  the  different  cases  shown  to  the 
problem  in  hand,  and  it  is  possible  to  combine  the  different 
parts  in  an  almost  endless  variety  of  ways. 


BENDING  DIES. 

6.  Simple  Bending  Dies. — A simple  form  of  bend- 
ing die  is  shown  in  Fig.  5.  Here  the  upper  and  lower  die 


are  so  formed  that  when  the  upper  is  forced  down  on  the 
blank  strip  of  stock  a , indicated  by  dotted  lines,  it  will  be 
bent  to  the  required  shape.  In  a bending  die,  some  form  of 
a gauge  or  stop  is  necessary  in  order  to  locate  the  blank 
properly;  this  must  be  made  to  suit  the  shape  thereof,  and 
in  its  simplest  form  may  be  a shoulder,  as  shown  at  b. 


§30 


DIES  AND  DIE  MAKING. 


7 


Fig.  6. 


When  the  piece  bent  by  bending  dies,  as,  for  instance, 
that  shown  in  Fig.  6,  is  examined,  it  will  be  found  to  have  a 
shape  slightly  different  from  that  of 
the  die.  Thus,  if  the  dotted  lines  , 

represent  the  shape  of  the  piece  while 
between  the  faces  of  the  dies,  on 
removal  it  will  assume  the  shape 
shown  in  the  full  lines,  by  reason  of  the  elasticity  of  the 
material.  Hence,  it  follows  that  for  elastic  materials  the 
bending  surfaces  must  be  arranged  to  bend  slightly  beyond 
the  required  angle;  how  much  beyond  must  be  determined 
by  experiment  in  each  particular  case.  In  general,  the 
amount  will  be  least  for  comparatively  non-elastic  materials, 
as  annealed  iron,  copper,  or  brass,  and  most  for  more  per- 
fectly elastic  metals,  as  spring  steel,  hard  brass,  etc.  With 
metals  like  lead  no  allowance  need  be  made. 

When  making  any  die  for  a forming  operation,  it  is  to  be 
observed  that  the  lower  and  upper  die  cannot  have  the  same 
shape.  This  is  shown  in  Fig.  7,  where  a comparatively  thick 

piece  of  material  c is  shown 
between  the  bending  sur- 
faces of  the  upper  die  a 
and  the  lower  die  b.  Evi- 
dently, the  upper  die  must 
have  on  its  bending  sur- 
face a curve  of  a radius 
equal  to  that  of  the  lower 
die  increased  by  the  thick- 
ness of  the  material.  Due 
attention  must  be  paid  to 
this  fact  when  making  any 
kind  of  a forming  die.  It  is  also  to  be  observed  that  any 
material  will  bend  more  easily  around  a curve  than  around 
a sharp  corner,  and  at  the  same  time  there  is  less  liability  of 
forming  a crack  at  the  exterior  surface  of  the  bend.  For 
this  reason,  the  corners  of  the  bending  surfaces  should  be 
rounded  off.  When  the  substance  to  be  bent  is  thin  and 
ductile,  very  little  rounding  off  is  needed;  the  harder  and 


8 DIES  AND  DIE  MAKING.  § 30 

thicker  the  material,  the  more  rounding  must  be  given,  in 
order  to  prevent  a crack  from  forming  in  the  bend. 

7.  Special  Bulldozer  Dies. — Fig.  8 shows  a form  of 
automatic  die  that  is  admirably  adapted  for  use  in  a bull- 
dozer. The  wings  w9  w of  the  die  a are  folded  in  by  the 


die  d , thus  bending  the  iron  without  stretching  it.  The 
part  d acts  simply  as  a cam  to  move  the  wings  of  the  die. 
The  illustration  shows  a piece  of  stock  b,  with  the  wings  w,  w 
closed  about  it;  the  dotted  lines  at  w\  w'  show  the  position 
of  the  wings  when  the  die  is  open.  When  working  cold 
metal,  if  the  punch  c is  made  with  parallel  sides,  as  in  the 
figure,  the  work  will  not  come  out  parallel,  as  at  b and  b\ 
but  will  be  somewhat  divergent,  as  at  e,  on  account  of  the 
elasticity  of  the  metal.  To  overcome  this,  the  punch  must 
be  made  with  its  edges  a little  convergent,  so  that  the  work 
when  closed  will  have  somewhat  the  appearance  of  the  piece 
shown  at  f.  The  subsequent  expanding  when  released  will 


DIES  AND  DIE  MAKING. 


9 


§ 30 

restore  it  to  a parallel  form.  The  amount  of  this  divergence 
depends  on  the  kind  of  metal  and  the  amount  that  it  is  heated. 
If  entirely  red  hot  when  finished,  it  will  act  something  like 
lead,  which  is  practically  non-elastic.  As  the  metal  is  partly 
cooled  when  compressed  between  the  cold  or  nearly  cold  dies, 
it  may  not  have  the  exact  form  of  the  die  when  cold. 

The  machine  termed  a bulldozer  is  really  a special  hori- 
zontal press  used  chiefly  for  bending  work.  The  term  auto- 
matic as  used  in  connection  with  dies  is’ not  strictly  correct, 
but  seems  to  be  the  word  generally  employed  in  dies  having 
some  of  their  working  surfaces  arranged  to  slide,  swing,,  or 
otherwise  move  in  relation  to  the  other  working  surfaces. 
This  form  of  construction  is  often  used  where  a number  of 
suboperations  are  performed  by  one  motion  of  the  press  ram. 
Some  of  these  motions  may  perhaps  be  at  right  angles  to  the 
general  line  of  motion.  The  presence  of  spring  knock-outs 
or  ejectors  would  not  entitle  a die  to  be  called  automatic. 

8.  Embossing  Dies. — The  working  surfaces  of  em- 
bossing dies  must  follow  the  design  of  the  raised  pattern 
to  be  produced.  Some  of  them  are  of.  hardened  steel  and 
some  of  an  alloy  of  lead  and  tin.  Sometimes  one  is  hard  and 
the  other  soft-cast  or  hammered  into  it.  Many  degrees  of 
hardness  or  accuracy  may  be  embodied,  according  to  the 
material  worked,  the  production  required,  and  the  artistic 
quality  of  the  arti- 
cle produced. 

9.  Simple  Em- 
bossing Dies. 

One  of  the  simplest 
designs  of  embos- 
sing die  is  shown  in 
Fig.  9,  where  the 
raised  outline  of  the 
work  is  cut  into  one 
of  the  dies  and  the 
other  is  worked  out 
to  suit  the  inside  of  the  raised  projection  of  the  work.  This 


10 


DIES  AND  DIE  MAKING. 


§ 30 


is  all  done  by  ordinary  lathe  work,  the  product  being  a 
circular  bead. 

Such  dies  may  readily  be  made,  however,  to  cut  the  blank 
and  do  the  embossing  in  one  operation,  as  in  the  combina- 
tion dies  already  described.  If  this  is  done,  the  punch 
should  not  have  any  projections  extending  beyond  the  plane 
of  the  cutting  edge.  If  there  are  such  projections,  they  will 
strike  the  stock  before  the  cutting  edges  cut  the  blank,  and 
the  latter,  in  consequence  of  this,  will  be  buckled  and  drawn 
out  of  sh'ape.  An  ejector  will  usually  have  to  be  fitted  to  a 
combined  cutting  and  embossing  die.  This  may  be  spring- 
actuated,  or  be  positively  operated  by  some  moving  part  of 
the  press,  as  is  most  convenient. 

lO.  Seaming  Dies. — Seaming  dies  are  merely  made 
to  fit  the  inside  and  outside  of  a can,  a bucket,  or  a pan,  at 
the  place  where  a folded-together  joint  occurs.  They  mash 
this  joint  down  tighter,  one  die  usually  having  a smooth  face 
and  the  other  a grooved  face  fitting  the  projecting  seam. 

A pair  of  such  dies,  for  an  outside  seam  on  a can  body, 
are  shown  in  Fig.  10 ; a is  the  upper  die  and  b the  lower  die, 

the  latter  being  mounted  in  a 
horn  c that  may  be  inserted  in  a 
press  of  proper  form.  If  the  seam 
is  to  project  inside  the  work,  then 
the  upper  die  must  have  a smooth 
concave  face  and  the  lower  die 
must  be  grooved.  A sample  of 
the  work  is  shown  at  d. 

11.  Curling. — The  curling 

process  may  be  defined  as  one  in 
which  the  end  of  each  element  of 
a hollow  object,  as  a cylinder  or 
truncated  cone,  with  walls  of  uni- 
form thickness,  is  bent  either 
outwards  or  inwards  into  an 
approximate  circle,  thus  forming  a hollow  ring  at  the  end  of 
the  object.  Its  general  form  is  that  of  a long  cylinder  of 


DIES  AND  DIE  MAKING. 


11 


§ 30 

small  diameter,  with  its  axis  bent  around  to  meet  itself  and 
with  a contour  parallel  to  that  of  the  periphery  of  the  object 
to  be  curled.  It  may  be  either  inside  or  outside,  according 
to  the  requirements  of  the  case.  Curling  differs  from  form- 
ing, because  the  metal  is  not  simply  pressed  into  place,  but 
is  forced  to  travel  of  itself  in  a predetermined  path  limited 
by  the  concave  curve  in  the  die  that  it  must  follow.  Each 
element  of  the  cylinder,  or  other  shaped  shell,  must  travel 
in  this  path  and  no  other,  with  its  end  acting  as  a lever  to 
start  bending  the  oncoming  portions  behind.  It  cannot  bend 
down  with  a sudden  angle,  thus  forming  a flat  surface  acting 
as  a single  bar,  because  all  its  neighbors  are  attached  together 
to  unite  in  resisting  circumferential  stresses. 

12.  Wiring. — The  term  wiring  is  often  used  as  a 
synonym  of  curling,  from  the  fact  that  curling  is  often  per- 
formed so  as  to  enclose  a ring  of  wire,  thus  giving  compara- 
tively great  stiffness  to  the  top  edge  of  the  object  so  finished. 
This  may  be  a tin  cup,  a coffee  pot,  a bucket,  or  a dish  pan. 
Some  of  these  utensils  are  cylindrical  and  others  conical,  and 
they  may  have  the  large  end  at  the  bottom  or  the  top.  In 
some  cases  the  horizontal  cross-section  of  the  object  may 
not  even  be  circular,  but  rather  elliptical,  or  angular  with 
rounded  corners. 

13.  False  Wiring. — This  is  a name  known  to  the  tin- 
ware trade,  and  rneans  wiring  with  the  wire  left  out,  i.  e., 
simply  curling.  It  is  not  often  used,  however,  in  describing 
goods.  These  are  supposed  to  be  wired  in  any  case,  and 
oftentimes  are  of  such  design  as  to  be  good  enough  with  an 
empty  curl. 

1 4.  Dies  for  Curling. — A design  for  curling  dies  is 

shown  in  Fig.  11,  which  is  intended  to  curl  a rim  a , Fig.  12, 
around  the  open  end  of  a piece  of  hollow  ware.  Referring 
to  Fig.  11,  the  upper  die  a has  a projection  that  fits  the 
inside  of  the  work,  and  a semicircular  groove  in  its  face  at 
the  base  of  the  projection,  as  shown  at  b.  The  upper  end  of 
the  lower  die  c is  recessed  to  receive  the  rim,  and  the  inclined 
surface  of  the  recess  assists  in  rolling  it  inwards.  This  is 


12 


DIES  AND  DIE  MAKING. 


§30 


shown  to  a larger  scale  in  Fig.  12,  where  the  rim  is  fully 
formed.  The  diameter  of  the  curl,  or  rim,  that  can  be 
produced  is  rarely  over  inch  for  a good  quality  of  tin 


fig.  ii. 


plate;  if  a larger  rim  is  produced,  the  metal  will  have  to 
stretch  so  much  that  it  will  tear.  If  it  is  well  annealed  and 

has  not  been  hardened  by 
any  previous  drawing, 
forming,  or  embossing 
operation,  a much  larger 
rim  can  sometimes  be 
curled.  When  the  work  is 
of  such  shape  that  it  cannot 
readily  be  removed  with 
the  fingers  from  the  lower 
die,  an  ejector,  asd,  Fig.  11, 
may  be  used  to  advantage. 
The  same  die  may  also  be 
used  for  curling  the  edge  of  the  work  over  a wire  ring. 

1 5.  Tapering  Curling  Dies. — Tapering  curling  dies 
are  shown  in  Fig.  13,  arranged  for  wiring  the  top  of  a rather 
deep  dish  pan.  The  lower  die  (a)  is  simply  a cast-iron 


§ 30 


DIES  AND  DIE  MAKING. 


13 


container  fitting  the  outside  of  the  pan,  grooves  being  pro- 
vided at  c and  d for  the  outwardly  projecting  seams — it  being 
a case  of  pieced  ware,  rather  than  a drawn  pan.  The  upper 
die,  shown  at  ( b ),  is  upside  down  and  is  usually  made  of  an  iron 
body  e with  a steel  ring  f (secured  to  it  by  screws)  to  form 
the  grooved  working  surface  that  does  the  curling.  In  this 
case  the  working  ring  is  divided  into  several  sections  by  nar- 
row radial  slits,  that  it  may  be  collapsible  and  thus  may 
crawl  into  a smaller  diameter,  as  it  descends  into  the  decreas- 
ing conical  pan.  For  conical  work  that  is  smallest  at  the 
top,  like  coffee  pots,  etc.,  this  action  is  reversed,  and  the  slit 


ring  expands  as  it  goes  down.  It  of  course  starts  with  the 
sections  in  contact  in  this  latter  case.  In  both  cases,  the 
return  of  the  ring  to  its  normal  size  is  performed  by  a num- 
ber of  spiral  springs  set  radially  in  the  plate  of  the  die.  For 
parallel-sided  work,  the  curling  ring  can  obviously  be  solid, 
as  it  need  not  change  its  diameter.  This  is  shown  in  Fig.  11, 
the  work  being  in  the  nature  of  a tin  cup  or  a dinner  pail. 

Where  curled  work  is  of  much  depth,  the  lower  die  is  usu- 
ally made  to  swing  or  slide  forwards  for  inserting  and  remov- 
ing the  work,  thus  avoiding  the  necessity  of  a very  long 
stroke  in  the  press  ram. 


IB.  Drawing. — In  a certain  sense,  drawing  is  an 
extension  of  the  forming  process.  It  differs  from  it  chiefly 
in  the  fact  that  an  outer  zone  of  the  flat  blank  that  is  required 
to  be  formed  into  a hollow  shape  is  confined  between  two 
rigid  flat  surfaces  in  such  a manner  that,  as  it  is  drawn 
radially  inwards  from  between  them,  no  wrinkles  can  form. 


d 


(a)  (b) 


Fig.  13. 


THE  DRAWING  PROCESS 


14 


DIES  AND  DIE  MAKING. 


§ 30 

The  products  are  a variety  of  cup-like  forms  of  cylindrical, 
conical,  and  approximately  hemispherical  shapes.  Some- 
times these  have  at  the  open  end  a flat,  outwardly  projecting 
flange;  then  the  general  shape  may  be  termed  hat-like. 

17.  Object  of  Drawing. — When  an  attempt  is  made 
to  form  a rather  deep  article  from  a blank  in  forming  dies, 

the  edges  of  the  blank  commence  to 
wrinkle,  and  in  extreme  cases  will 
even  fold  up  so  that  the  folds  will  lie 
over  each  other.  These  folds,  as  the 
wrinkles  may  be  called,  are  well 
shown  in  Fig.  14,  which  is  an  illus- 
tration of  a tin-can  cover  that  has 
been  produced  by  forming  dies. 
Inspecting  it  closely,  it  will  be  seen  that,  for  a short  distance 
above  the  bottom,  the  sides  of  the  rim  are  smooth.  Farther 
up  the  wrinkles  commence  to  form,  and  gradually  become 
larger  toward  the  upper  edge.  It  is  not  known  who  first 
discovered  that  if  an  annular  zone  of  the  blank  is  confined 
between  two  flat  surfaces  strongly  pressed  together  by 
springs  or  other  means,  and  that  if  the  metal  is  then  drawn 
out  from  between  them,  no  wrinkles  will  be  formed.  The 
piece  pressed  down  on  the  blank,  holding  it  in  place,  is  called 
the  blank  bolder.  This  discovery  is  of  comparatively 
recent  origin,  but  has  proved  of  a far-reaching  influence  in 
the  cheap  production  of  many  articles,  especially  household 
goods,  such  as  pots,  kettles,  dippers,  and  pans. 

18.  Redrawing. — The  process  of  redrawing  is  an 

extension  of  the  drawing  process;  in  other  words,  it  is  simply 
the  drawing  process  repeated  in  order  to  deepen  the  hollow 
shape  formed  by  drawing.  In  the  redrawing,  the  diameter 
is  reduced  at  the  same  time  that  the  length  is  increased. 
Sometimes  this  redrawing  is  repeated  several  times,  perhaps 
a dozen  or  more.  The  work  then  assumes  more  the  appear- 
ance of  a tube  than  a cup,  one  end  of  course  being  closed. 
Both  drawing  and  redrawing  dies  having  a blank  holder  to 
prevent  wrinkles  are  known  as  double-action  dies.  The 


DIES  AND  DIE  MAKING. 


15 


§ 30 

special  motion  of  the  blank  holder  may  in  certain  cases  be 
obtained  by  springs  in  a single-action  press.  In  most  cases, 
however,  a double-action  press  must  be  used,  having  a special 
motion,  followed  by  a dwell , that  is,  a pause,  for  the  ram, 
while  the  plunger  inside  the  ram  continues  its  stroke. 


DRAWING  DIES. 

ID.  The  Spring  Drawing  Dies.  — The  spring 
drawing  dies  shown  in  Fig.  15  are  intended  to  draw  the 


Fig.  15. 

same  piece  that  was  illustrated  in  Fig.  1 ( b ).  Referring  to 
Fig.  2,  it  is  seen  that  the  lower  dies  are  identical.  The 


16 


DIEvS  AND  DIE  MAKING. 


§ 30 


upper  die,  or  punch,  is  surrounded  by  the  blank  holder  a , 
which  is  held  to  its  lowest  position  by  a powerful  helical 
spring  b.  The  punch  is  free  to  slide  through  the  blank 
holder,  when  the  latter  comes  to  rest  by  reason  of  coming 
in  contact  with  the  blank  lying  in  the  gauge  ring;  to  allow 
this  to  occur,  the  stem  of  the  blank  holder  is  slotted,  as 
shown  at  c,  where  a cylindrical  pin  d in  the  side  of  the 
punch  forms  a stop  for  the  blank  holder.  As  the  punch 
descends,  the  blank  holder  strikes  and  the  spring  is  com- 
pressed before  the  punch  strikes  the  blank;  as  it  continues 
to  descend,  the  annular  zone  confined  between  the  lower 
surface  of  the  blank  holder  and  the  upper  surface  of  the  die 
is  gradually  drawn  radially  inwards,  and,  passing  over  the 
rounded  upper  edge  of  the  die,  is  formed  into  a rim  without 
any  wrinkles.  Obviously,  the  metal  is  compressed,  or  upset , 
circumferentially,  while  being  stretched  radially,  its  thick- 
ness remaining  about  the  same. 

The  work  appears  in  different  stages  in  Fig.  16,  where  (a) 
shows  a cross-section  of  the  blank,  (b)  shows  the  cross- 
. section  when  the  punch  has  partially  en- 
tered the  die,  and  (<r)  shows  the  work  when 
the  punch  is  fully  in  the  die.  The  work  is 
stripped  off  the  punch,  as  it  moves  up,  by 
the  sharp  lower  edge  of  the  die. 

If  the  rim  formed  by  the  drawing  opera- 
tion shows  wrinkles,  it  indicates  that  the 
pressure  with  which  the  outer  zone  of  the 
blank  was  held  was  insufficient.  The  rem- 
edy is  to  stiffen  the  spring  or  substitute  a heavier  one.  On  the 
other  hand,  if  the  punch  tears  through  the  blank,  the  spring 
is  too  stiff,  and  must  either  be  eased  or  a weaker  one  made. 

It  is  essential  to  successful  drawing  that  the  working  parts 
of  the  die  be  highly  polished,  and  that  the  material  to  be  drawn 
be  soft.  The  depth  to  which  a cup  can  be  drawn  in  one  oper- 
ation depends  on  the  ductility  of  the  material;  with  well- 
annealed  copper,  a depth  equal  to  two-thirds  the  diameter  is 
often  obtained.  Experiment  alone  can  determine  for  each 
particular  case  what  depth  can  be  attained  by  one  drawing 


(a) 


Q>) 


(C) 

Fig.  16. 


separate  operations  must  be  performed,  namely,  cutting  and 
drawing.  When  a large  number  of  pieces  are  to  be  drawn, 


§ 30  DIES  AND  DIE  MAKING.  17 

operation.  The  depth  relatively  to  the  diameter  depends 
much  on  the  thickness,  as  well  as  the  quality,  of  the  material. 

20.  Combination  Cutting-Drawing  Dies  on  Plain 
Work. — It  is  obvious  that  for  making  a cup  as  shown,  two 


Fig.  17. 


18 


DIES  AND  DIE  MAKING. 


30 


however,  dies  may  be  designed  that  will  cut  the  blank  and 
form  the  cup  in  one  operation,  thus  greatly  reducing  the 
time  cost  per  piece.  Such  dies  will  be  about  twice  as  expen- 
sive as  two  single  pairs  of  dies. 

A variety  of  combination  spring  drawing  dies  is  shown 
in  Fig.  17,  which  is  intended  to  draw  the  same  piece  that  was 
shown  in  Fig.  1 ( b ).  Referring  to  Fig.  17,  a is  a lower  chuck 
holding  the  die  which  is  bored  to  the  diameter  of  the 
blank,  with  its  upper  edge  sharp.  The  blank  is  cut  out  by 
the  punch  c,  the  outer  edge  of  which  is  also  sharpened  to 
form  a cutting  edge.  The  punch  is  bored  centrally  to  the 
outside  diameter  of  the  cup,  and  the  inner  edge  is  nicely 
rounded.  An  ejector  d,  actuated  by  the  helical  spring 
shown,  serves  to  push  the  cup  from  the  upper  die  in  case  it 
should  stick  there.  This  is  free  to  move  in  the  direction  of 
its  axis,  and  is  confined  as  to  its  lowest  position  by  a shoulder 
in  the  cutting  punch  and  an  abutting  flange  of  its  own. 

The  blank  holder  e is  placed  within  the  lower  die;  it  sur- 
rounds the  forming  punch  f,  which  is  stationary  in  this  case. 
The  blank  holder  also  serves  to  strip  the  finished  cup  from 
the  punch.  The  pressure  on  the  blank  holder  is  obtained 
from  a helical  spring  placed  below  the  chuck;  this  spring 
operates  on  a movable  sleeve  g with  a large  flange  in  which 
pins  i,  i are  carried.  These  pins  pass  freely  through  holes 
in  the  chuck  and  the  flange  of  the  punch;  they  abut  against 
the  lower  surface  of  the  blank  holder,  which  is  thus  actuated 
by  the  spring.  The  lower  die  must  be  provided  with  a 
suitable  guide  strip,  gauge  pin,  and  stripper  for  the  stock, 
arranged  in  the  same  manner  as  for  any  ordinary  cutting 
die.  These  appurtenances  have  been  omitted  in  the  draw- 
ing for  the  sake  of  clearness. 

21.  The  Operation  of  Cutting-Drawing  Dies. — 

The  operation  of  these  dies  is  as  follows:  The  descending 
upper  die  cuts  the  blank  from  the  stock;  it  is  immediately 
gripped  by  the  blank  holder  and  confined  between  its  upper 
surface  and  the  lower  surface  of  the  cutting  punch,  the 
spring  below  the  bolster  giving  the  pressure  necessary  to 


DIES  AND  DIE  MAKING. 


19 


30 


prevent  wrinkling  during  the  drawing.  As  the  upper  die 
keeps  on  descending,  the  blank  and  blank  holder  are  car- 
ried down  until  they  strike  the  upper  surface  of  the  forming 
punch  f ; the  outer  zone  of  the  blank  is  then  gradually 
pulled  out  and  the  cup  is  formed  around  the  punch.  The 
appearance  of  the  work  in  successive  stages  is  the  same  as  was 
shown  in  Fig.  16,  except  that  the  work  will  be  bottom  side  up. 

In  order  that  the  blank  holder  may  be  inserted,  the  lower 
die  and  forming  punch  must  be  made  separate.  They  may 
then  be  connected  together  in  any  convenient  way  that  will 
insure  proper  centering,  as,  for  instance,  by  providing  the 
punch  with  a threaded  flange  screwed  into  a threaded  recess 
of  the  die,  as  shown.  All  spring-drawing  dies  are  intended 
to  be  used  in  single-action  presses , although  they  are  double- 
action dies. 


22.  When  a double-action  press  is  available,  a very  much 
simpler  design  of  drawing  dies  is  possible.  Such  a press  is 
provided  with  two  rams  working  within  each  other,  and 
independently  adjustable.  The  outer  ram,  conveniently 
termed  simply  the  rani , is  so  actuated  that  for  a certain 
period  of  the  revolution  of  the  press  shaft  it  will  be  at  rest. 
The  inner  ram  may  properly  be  termed  the  plunger.  It 
continues  its  downward  motion,  giving  a certain  excess 
travel,  by  which  is  measured  the  attainable  depth  of  work. 
Fig.  18  shows  a design  of  drawing  dies  for  a double-action 
press,  intended  to  form  the  cup  shown  in  Fig.  1 ( b ).  Refer- 
ring to  the  illustration,  a is  a chuck  bored  to  receive  the 
drawing  die  b,  and  threaded  to  receive  the  cutting  die  c. 
To  insure  correct  location  of  the  two  dies  with  reference  to 
each  other,  the  one  may  be  recessed  to  fit  a central  project- 
ing shoulder  of  the  other,  as  shown.  The  two  dies  may  be 
rigidly  held  together  by  any  convenient  means ; for  instance, 
the  outside  of  the  cutting  die  may  be  threaded,  and  suitable 
holes  may  be  provided  to  receive  a wrench,  as  shown  in  the 
illustration. 

The  upper  die  d , which  is  the  blank  holder  and  at  the 
same  time  the  cutting  punch  for  the  blank,  is  fitted  to  the 

C.  S.  III.— 42 


20 


DIES  AND  DIE  MAKING. 


§ 30 


ram,  and  the  inner  part,  or  drawing  punch  e , is  fitted  to 
the  plunger.  The  ram  is  so  adjusted  that  when  d has 
descended  and  is  at  rest,  it  is  close  enough  to  hug  the  blank 
confined  between  its  lower  surface  and  the  upper  surface  of 
the  die,  and  thus  furnish  the  pressure  necessary  to  prevent 
wrinkling.  The  drawing  punch  is  to  be  so  timed  that  it  will 
not  strike  the  blank  until  it  has  been  confined  by  the  blank 


Fig.  18. 

holder.  The  cup  is  then  drawn  by  the  punch.  The  finished 
cup  is  stripped  off  by  the  sharp  lower  edge  of  the  drawing 
die.  This  kind  of  a die  is  comparatively  inexpensive ; the 
price  should  not  exceed  50  per  cent,  more  than  plain 
drawing  dies  that  do  not  cut;  it  should  be  considerably  less 
than  that  of  cutting-drawing  dies  for  a single-action  press, 
where  spring  action  must  be  provided. 


DIES  AND  DIE  MAKING. 


21 


§ 30 

23.  Drawing  Work  With  Tapering  or  Curved 

Walls. — So  far,  only  the  drawing  of  cups  with  walls  at  a 
right  angle  to  a flat  surface  has  been  considered.  It  is  pos- 
sible to  draw  work  with  tapering  or  curved  walls,  however, 
as,  for  instance,  the  work  shown  in  cross-section  between 
the  upper  and  lower  dies  of  Fig.  19.  In  this  case,  a flange 


is  left  on  the  open  end  of  the  work,  which  is  done  by  not 
drawing  the  metal  entirely  from  between  the  blank  holder  b 
and  the  upper  surface  of  the  drawing  die  a.  The  die  shown 
is  a combined  cutting  and  drawing  die;  the  cutting  edge  of 
the  lower  die  is  formed  on  a removable  ring  c , and  hence  is 
easily  renewable  in  case  of  wear  or  accident.  To  eject  the 


22 


DIES  AND  DIE  MAKING. 


§ 30 

drawn  work  from  the  lower  die,  an  ejector  d may  be  fitted. 
This  may  be  spring-actuated,  as  shown,  or  it  may  be  posi- 
tively operated  by  some  moving  part  of  the  press.  Whether 
or  not  an  ejector,  often  known  as  a knock-out , is  to  be  fitted 
depends  on  the  shape  of  the  work.  In  many  cases  this  is 
such  that  it  can  easily  be  lifted  out  of  the  lower  die;  in  that 
ease,  the  ejector  may  be  omitted.  Drawing  dies  for  work  as 
shown  need  not  always  be  made  of  tool  steel.  In  many 
cases  they  may  be  made  advantageously  of  close-grained 
cast-iron. 

The  particular  design  of  dies  shown  in  Fig.  19  is  intended 
for  a double-action  press.  It  is  also  possible  to  design  com- 
bination dies  for  the  same  work  to  use  in  a single-action 
press.'  Such  may  be  constructed  on  the  same  principles  as 
the  die  shown  in  Fig.  17. 

In  order  to  prevent  wrinkles  from  forming  in  the  walls  of 
work  having  a cross-section  similar  to  that  shown  in  Fig.  19, 
the  pressure  of  the  blank  holder  on  the  confined  outer  zone 
of  the  blank  must  be  quite  heavy.  If  wrinkles  cannot  be 
prevented  from  forming  in  the  body,  they  can  afterwards 
be  removed  by  roller-spinning  the  work  in  a suitable 
lathe. 


24.  Combined  Cutting,  Drawing,  and  Emboss- 
ing Die. — For  work  like  that  shown  in  Fig.  20  ( a ),  dies 
may  be  designed  that  will  cut  the  blank,  draw  the  rim,  and 
emboss  the  flat  top  in  one  operation,  thus  enormously  redu- 
cing the  time  cost  per  piece  below  what  it  would  be  in  case 
these  three  operations  were  performed  in  separate  dies. 
The  design  of  die  to  be  used  for  this  class  of  work  depends 
on  the  type  of  press  that’  is  available. 

For  a single-action  press,  the  design  shown  in  Fig.  20  ( b ) 
is  a satisfactory  one.  As  a matter  of  course,  this  may  be 
modified  in  various  ways  to  suit  conditions.  In  the  illustra- 
tion, the  dies  are  shown  hard  together,  with  the  work 
between  them;  when  the  dies  are  apart,  the  upper  ejector  a 
projects  beyond  the  face  of  the  embossing  punch  b.  The 
combined  blank  holder  and  ejector  c in  the  lower  die  is  then 


DIES  AND  DIE  MAKING. 


23 


§ 30 

in  its  uppermost  position.  The  pressure  necessary  for  suc- 
cessful drawing  is  supplied  by  a number  of  heavy  helical 
springs  that  may  extend  into  recesses  bored  into  the  blank 
holder  in  order  to  effect  a saving  in  the  height  of  the  die. 
For  the  same  reason,  the  springs  for  the  upper  ejector  may 


(bj 

Fig.  20. 


be  placed  within  recesses  bored  into  it,  if  circumstances  per- 
mit. The  lower  cutting  die  may  be  solid,  as  shown,  or  a 
small  tool-steel  ring  may  be  attached  to  a cast-iron  body. 
The  point  to  be  observed  in  making  any  kind  of  a combina- 
tion die  is  to  design  it  so  that  it  is  cheap  in  first  cost,  and 
that  all  wearing  parts  can  be  easily  and  cheaply  renewed. 


24 


DIES  AND  DIE  MAKING. 


§30 


When  a double-action  press  is  available,  these  dies  may  be 
designed  as  shown  in  Fig.  21.  Evidently  no  stripper  will  be 
needed  for  the  upper  die,  as  the  embossing  and  drawing 


punch  a will  automatically  strip  the  finished  work  from  the 
upper  die.  The  lower  embossing  die  b may  act  as  an  ejec- 
tor by  making  it  movable.  It  is  then  actuated  by  the  spring 
shown.  If  it  is  stationary,  then  an  ejector  may  rise  inside 


DIES  AND  DIE  MAKING. 


25 


§ 30 


of  it.  Comparing  Figs.  20  and  21,  it  is  seen  that  there  is 
far  less  work  required  to  make  the  dies  for  a double-action 
press.  The  design  shown  may  be  modified  in  various  ways, 
as  deemed  advisable  by  the  toolmaker.  Referring  again  to 
Figs.  20  and  21,  the  lower  die  should  be  fitted  with  a suitable 
guide  strip,  gauge  pin,  and  stripper  for  the  stock.  These 
have  been  omitted  in  the  drawing  for  the  sake  of  clearness. 

25.  Triple-Action  Drawing  Dies.  — Both  of  the 
designs  just  shown  will  discharge  the  finished  work  on  top 
of  the  lower  die.  In  many  cases  this  is  objectionable;  the 


Fig.  22. 


design  may  then  be  modified,  as  shown  in  Fig.  22,  if  circum- 
stances permit.  In  this  case,  the  lower  embossing  die  a is 
entirely  separate  from  the  drawing  die  b,  and  is  placed  some 
distance  below  it.  The  blank  holder  c cuts  the  blank  and 
holds  it;  the  drawing  and  embossing  punch  d first  draws  the 


26 


DIES  AND  DIE  MAKING. 


§30 

rim  of  the  work  and  finally  embosses  the  bottom.  As  the 
punch  ascends,  the  sharp  lower  edge  of  the  drawing  die  strips 
the  work  off  from  it.  The  work  then  falls  and  is  removed 
through  the  opening  e in  the  lower  die.  It  will  rarely  be 
necessary  to  fit  an  ejector  to  the  embossing  die.  Evidently, 
this  design  of  die  can  be  adopted  only  for  the  work  that  can 
be  pushed  laterally  clear  through  the  drawing  die. 

These  dies  are  of  the  general  class  known  as  triple- 
action, because  originally  the  lower  embossing  die  was 
operated  from  below  by  a separate  special  ram,  thus  making 
three  motions  to  the  press  instead  of  two.  The  present 
practice,  however,  is  usually  as  shown. 

Obviously,  the  stroke  of  the  press  plunger  must,  relatively 
to  the  ram  stroke,  be  longer  than  usual. 

26.  Discharge  of  Work  From  Dies. — The  lateral 

ejection  of  the  work,  through  the  doorway  e e,  Fig.  22,  at 
the  back  of  the  die,  is  sometimes  performed  by  a sliding 
pusher  rod  worked  by  the  press.  More  often,  however,  the 
press  is  set  in  an  inclined  position  of  some  40°  from  the  ver- 
tical, so  that  work  done  in  these  dies,  and  also  in  such  as  are 
shown  in  Figs.  3,  4,  17,  19,  20,  21,  and  22,  may  slide  out  by 
the  action  of  gravity. 


SIZE  OF  BLANKS  FOR  DRAWING  AND  FORMING. 

27.  Obtaining  the  Size  of  the  Blank  by  Trial. 

The  only  sure  method  of  getting  the  correct  size  or  shape  of 
a very  irregular  blank  that  is  to  be  subjected  to  a drawing  or 
forming  operation  is  a tentative  one.  Naturally,  it  is  likely 
to  prove  expensive.  A blank  is  cut  as  near  to  the  correct 
size  as  judgment  dictates;  it  is  then  drawn  or  formed  and 
the  results  are  observed.  A new  blank  is  then  prepared, 
modified  from  the  first  one  in  accordance  with  the  results 
obtained  in  the  first  trial.  This  is  then  drawn  or  formed, 
and  the  cycle  of  operations  repeated  until  the  correct  size 
and  shape  of  blank  are  obtained.  The  cutting  parts  of 
combination  dies  are  often  left  unfinished  while  the  drawing 


§30 


DIES  AND  DIE  MAKING. 


27 


parts  are  used  to  ascertain  the  cut  in  the  manner  just 
explained. 


28.  Rules  for  Size  of  Blank. — The  following  for- 
mula for  the  diameter  of  the  blank  in  cylindrical  work  will 
give  quite  a close  approximation  to  its  correct  size: 

Let  d — diameter  of  cylindrical  cup  in  inches; 
h = height  of  cup  in  inches; 
r — radius  of  corner  in  inches; 
x — diameter  of  circular  blank  in  inches. 


Then,  for  a sharp-cornered  cup,  as  shown  in  Fig.  23  ( a ), 


x = \/d*  + 4d  h.  (1.) 

Example. — Find  av  trial  diameter  of  blank 
for  a cup  to  be  drawn  1 inch  deep  and  2 inches 
in  diameter. 

Solution. — Applying  formula  1,  and  sub- 
stituting values,  we  get 

x = j/2*  + 4x2x1  = 3.464  in.  Ans. 

29.  For  a round-cornered  cup,  as 
shown  in  cross-section  in  Fig.  23  ($), 

x = 4/ <r/2  -f-  4 dh  — r,  (2.) 


Fig.  23. 


provided  the  radius  of  the  corner  is  not  more  than  the 
height  of  the  cup. 


Example. — Find  a trial  diameter  of  blank  for  a cup  having  a radius 
of  \ inch  to  the  round  corner,  when  the  height  of  the  cup  is  1 inch  and 
its  diameter  is  2 inches. 

Solution. — Applying  formula  2,  and  substituting  the  values,  we  get 
x — ^/22  + 4x2x1  — \ = 3.214  in.  Ans. 


30.  For  drawn  or  formed  work  that  is  not  cylindrical,  but 
circular  in  plan  view,  as,  for  instance,  that  shown  in  Fig.  24, 
the  following  method  may  be  used  for  obtaining  the  trial 
diameter  of  the  blank. 


28 


DIES  AND  DIE  MAKING. 


§ 30 

Make  a full-size  drawing  of  the  profile  that  is  to  be  formed, 
as  in  Fig.  24.  Commencing  at  the  intersection  of  the  axis 
with  the  profile,  and  to  one  side  of  the  axis,  step  off  divisions 
inch  long,  as  1,  2,  3 , Jf,  etc.  From  the  center  of  each 


Fig.  24. 


division  thus  stepped  off  measure  the  perpendicular  dis- 
tance, as  ra,  r„  rv  etc.,  to  the  axis  in  inches.  Add  the 
distance  and  extract  the  square  root  of  their  sum  to  obtain 
the  approximate  diameter  of  the  blank. 

Example. — Assuming  that  Fig.  24  is  a full-size  profile  of  the  work, 
what  would  be  the  trial  diameter  of  the  blank  ? 

Solution. — Measuring  the  distance  with  a decimal  scale,  they  are 
found  to  measure  .06,  .19,  .31,  .44,  .56,  .69,  .75,  .84,  .95,  1.06,  1.17,  1.24, 
1.31,  1.38,  1.48,  1.61,  1.70,  1.74  in.  Their  sum  is  17.41  in.,  and  the  square 
root  of  this  number  is  4.18,  which  is  the  approximate  diameter  of  the 
blank  in  inches.  Ans. 


REDRAWING  DIES. 

31.  Simple  Redrawing. — Redrawing  dies  do  not 

differ  essentially  from  ordinary  first-operation  drawing  dies, 
and  may  be  designed  in  the  same  manner  for  a single-action 
or  a double-action  press.  The  gauge  ring  is  to  be  made  to 
the  external  diameter  of  the  cup,  and  the  blank  holder  to  the 
inside  diameter.  The  appearance  of  the  cup  in  successive 


DIES  AND  DIE  MAKING. 


29 


8 30 


stages  of  the  drawing  and  redrawing  process  is  shown  in 
Fig.  25.  At  ( a ) the  blank  is  shown,  which  is  formed  into 
the  cup  shown  at  ( b ) by  plain  drawing  dies  or  combined  cut- 
ting and  drawing  dies.  The  cup,  after  annealing,  is  placed 
into  the  gauge  ring  of  the  redrawing  dies,  and  the  punch  in 
descending  pulls  the  metal  from  between  the  blank  holder 

and  the  upper  surface  of  the  drawing 

fa)  die,  first  into  the  shape  shown  at  (c), 

and  finally  into  that  of  an  elongated 
cup  shown  at  (< d ).  This  cup,  after 

' 1 * annealing,  may  be  redrawn  again,  its 

appearance  when  partially  redrawn 

I — * 1 being  shown  at  (e)  and  when  fully  re- 

'■"j  drawn,  at  ( f ).  The  greatest  amount 

L 1 that  the  diameter  of  a cup  can  be  re- 

duced in  each  drawing  operation  is 
usually  placed  at  two  fifths  of  the 
diameter.  Thus,  a cup  2 inches  in 
diameter  may  in 
one  drawing  be 
reduced  to  2 — 2 
X } = 1{  inches. 


(C) 


(d) 


(e) 


Experiment 
alone  will  deter- 
mine positively 
for  each  particu- 
lar case  if  this 
reduction  of  di- 
ameter can  b e 
obtained.  The 
amount  depends 
on  the  character 
of  the  metal  and 
the  thickness  of  the  sheet.  In  Fig.  26  is  shown,  in  a verti- 
cal section,  a pair  of  double-action  redrawing  dies  in  their 
simplest  form,  a being  the  blank  holder  and  b the  punch. 
These  are  suitable  for  drawing  (d)  into  (/),  as  shown  in 
Fig,  25. 


(f) 

Fig.  25. 


30 


DIES  AND  DIE  MAKING. 


§ 30 


32.  Reverse  Redrawing. — For  some  work,  a proc- 
ess known  as  reverse  redrawing  may  be  used  advan- 
tageously. Fig.  2 7 
shows  dies  for  reverse 
redrawing  designed 
for  a double-action 
press.  The  figure 
shows  between  the 
punch  and  die,  a cup 
that  is  partially  re- 
drawn; it  will  be  ob- 
served that  this  cup 
is  being  redrawn  in  a 
direction  the  reverse 
from  that  in  which  it 
was  drawn.  In  the 
illustration,  a is  the 
punch,  b the  blank 
holder  bored  to  fit  the 
outside  of  the  cup, 
and  c is  the  die,  the 
outside  of  which  is 
turned  and  polished 
Shapes  that  may  be 


fig.  27. 


to  fit  nicely  the  inside  of  the  cup. 


redrawn  by  reverse  redrawing  are  shown  in  Fig.  28;  these 
will  serve  to  suggest  others. 

In  Fig.  29  are  shown  in  vertical  section  five  stages  of 
drawing  a deep  cup  a.  The,  piece  at  the  end  of  the  first 
operation  is  shown  at  b and  c;  d and  e show  successive 


30 


DIES  AND  DIE  MAKING. 


31 


cup  is  shown  at  a. 
reduc- 


The  fifth 


Fig.  29. 


operations.  The  finished 
operation,  being  a small 
tion,  is  performed  by  single-action 
redrawing  dies. 

In  Fig.  30  (a)  is  shown  a simple 
form  of  single-action  redrawing 
dies,  such  as  would  be  suitable  for 
drawing  the  cup  shown  in  Fig.  29 
from  the  form  shown  at  e to 
that  at  a. 

In  Fig.  30  ( b ) is  shown  a typical  single-action  redrawing  die 
■=— =<  at  a , a punch  at  l \ and  a cartridge 

- shell  at  c.  Here  both  drawing  and 

broacliing  have  been  performed. 
The  latter  consists  of  squeezing 
thinner  the  walls  of  the  shell,  by 
making  the  space  between  punch 
and  die  too  small  for  the  metal. 
In  this  case  the  punch  is  conical 
and  the  walls  of  the  shell  thinner 
at  the  top  end.  Even  if  parallel, 
they  can  be  made  thinner  than  the 
original  metal  at  the  bottom  of  the 
cup  if  desired. 


ently  non-ductile  flow 


COINING  PROCESSES. 

33.  Application  of  the 
Coining  Process.- — The  process 
of  coining  consists  in  so  pressing 
or  mashing  the  material  that  its 
particles  start  to  flow  in  any  or 
all  directions,  following  the  lines 
of  least  resistance.  Obviously, 
brittle  materials  cannot  be  treated 
in  this  way  to  much  extent,  al- 
though some  substances  appar- 
in  a remarkable  way.  Instances  of 


32 


DIES  AND  DIE  MAKING. 


§ 30 

this  are  shown  in  the  action  of  glaciers,  where  the  solid  ice 
flows  down  through  valleys  at  a very  slow  rate,  entirely 
changing  its  shape  through  years  or  centuries  of  action, 
without  crumbling,  but,  on  the  other  hand,  acting  after  the 
manner  of  a liquid  of  great  viscosity. 

Another  instance  of  such  action  is  seen  in  a cake  of 
pitch,  through  which  stones  will  gradually  sink  by  their  own 
weight,  at  a very  slow  rate  of  motion,  the  pitch  closing 
over  them  intact,  as  if  it  were  a jelly-like  material. 

Under  ordinary  circumstances,  however,  such  substances 
as  hardened  steel,  cast  iron,  pitch,  chalk,  or  ice,  commonly 
supposed  to  be  brittle,  do  crumble  when  subjected  to  pres- 
sure beyond  their  elastic  limit.  The  ductile  metals  and 
some  other  substances,  such  as  clay,  wax,  butter,  etc.,  are 
legitimate  subjects  of  the  coining  process.  Such  ductile 
metals  as  steel,  iron,  copper,  etc.  will  flow  farther  and  under 
very  much  less  pressure  if  heated  red  hot  than  if  cold. 
Hence,  all  the  ordinary  operations  of  forging,  from  the 
rolling  mill  and  steam  hammer  down  to  the  country  black- 
smith shop,  are  performed  with  the  metal  heated  to  redness. 
In  the  coining  process  as  applied  to  practical  arts,  these 
flowing  materials  are  usually  confined  in  dies  or  molds  of 
some  kind  to  bring  them  to  the  desired  shape.  The  products 
of  such  molds  are  very  familiar  to  the  public  when  in  the 
shape  of  cakes  of  soap  or  pats  of  butter;  but  exactly  the 
same  principles  are  applied  in  the  coining  of  money,  which 
concerns  certain  metals,  such  as  gold,  silver,  bronze,  nickel, 
aluminum,  etc. 

In  that  process  of  the  art,  which  is  technically  called  coin- 
ing, the  products  of  which  are  usually  coins  of  the  realm, 
medals,  or  badges  of  various  sorts,  the  metal  is  worked  cold. 
The  two  impressions  on  the  obverse  and  reverse  sides  of  the 
coin  are  made  by  dies  engraved  with  the  proper  design, 
working  in  a so-called  collar.  The  collar  confines  the  metal 
from  spreading  too  far  edgewise  and  serves  as  a mold  for 
the  edges.  These  may  be  smooth,  as  in  American  cents,  or 
reeded  with  small  grooves,  as  in  American  silver  coins  of 
various  sizes.  In  order  to  give  a thickened  rim,  and  to  insure 


DIES  AND  DIE  MAKING. 


33 


§ 30 

the  rounded  corners  that  are  desirable  for  beauty  and  for 
smoothness,  the  disk  of  metal  from  which  a coin  is  to  be 
made  is  milled  on  the  edges.  This  process  consists  in  roll- 
ing the  coin  between  grooved  jaws  so  as  to  form  a thickened 
and  well-rounded  rim.  In  this  form  it  is  called  a plancliet. 
The  pressure  of  the  dies  causes  the  metal  to  flow  into  and 
fill  all  the  spaces  that  form  the  inscriptions  and  ornamental 
or  emblematical  designs,  and  also  to  force  the  metal  out 
sidewise  to  fill  the  collar  and  form  any  reeding  or  lettering 
that  may  be  cut  on  the  rim.  Were  the  pressure  too  great, 
the  metal  would  flow  up  into  the  small  apertures  between 
the  dies  and  collar,  forming  a thin  fin  projecting  at  right 
angles  to  the  face  of  the  coin.  The  action  of  the  dies  must 
therefore  be  limited,  so  as  to  stop  before  this  thin  fin  com- 
mences to  form. 

34.  Coining  Dies. — In  Fig.  31  is  shown  at  (a),  in  ver- 
tical section,  a pair  of  coining  dies,  the  collar  surrounding 


the  lower  die  being  in  its  natural  position  at  the  time  when 
the  upper  die  has  risen  out  of  the  way,  and  the  lower  die 
has  risen  enough  into  the  collar  to  eject  the  finished  coin 
and  allow  it  to  be  taken  off  by  the  fingers  in  case  of  hand 
feeding,  or  swept  off  by  the  next  incoming  planchet  if  the 
press 'happens  to  be  automatic.  At  ( b ) is  shown  the  same 


34 


DIES  AND  DIE  MAKING. 


§30 

dies  when  in  closed  position  at  the  time  the  impression  is 
being  made.  Obviously,  the  space  between  them  and 
between  the  sides  of  the  collar  represents  the  exact  size  and 
shape  of  the  coin,  with  the  exception  of  the  rounded  corners 
previously  referred  to. 

Such  dies  may  be  made  for  coins  of  other  than  circular 
contour,  as  elliptical,  octagonal,  etc. 

35.  Drop  Forgings. — When  a number  of  forgings  of 
the  same  pattern  are  to  be  made,  the  work  is  often  done  by 
driving  or  pressing  the  metal  into  a lower  die  by  the  action 
of  a flat-faced  die  set  in  the  ram  of  a drop  hammer.  The 
metal  is  usually  red  or  white  hot,  especially  if  it  is  iron  or 
steel.  This  process  is  called  drop  forging,  although 
sometimes  the  products  are  made  by  so-called  forging 
presses  with  a number  of  blows  from  a positively  driven 
short-stroked  ram,  rather  than  by  the  fall  of  a heavy  ram  with 
a long  stroke.  It  is  frequently  shaped  by  several  sets  of 
dies  before  it  has  acquired  the  desired  form,  or  the  work  is 
roughly  formed  by  hand  and  then  finished  in  the  dies. 

36.  D ies  for  Drop  Forging. — Fig.  32  (a)  shows  a set 
of  dies  that  may  be  used  in  drop  forging  the  wrench  shown 
in  Fig.  32  ( b ).  The  end  of  a bar  of  iron  is  upset  to  gain 
stock  for  the  head  of  the  wrench ; this  may  be  done  by  hand 
or  in  a machine.  The  bar  is  then  put  into  the  first  die  a , 
which  acts  like  a fuller  and  spreads  the  iron  at  the  point 
out  toward  the  edges.  The  handle  is  partly  formed  in  this 
die.  The  partly  finished  piece,  which  is  shown  at  f9  is  then 
put  into  the  second  die  b , and  the  handle  finished  and  the 
metal  in  the  head  pressed  well  into  the  die.  When  the 
forging  is  taken  from  this  die  it  has  the  form  g of  the  fin- 
ished wrench,  but  the  fin  of  metal  h that  squeezed  out  of 
the  die  is  still  attached  to  it.  This  fin  is  sheared  off  by  the 
trimming  die  c,  which  is  really  a punch,  the  portion  d fitting 
into  the  die  c for  this  purpose.  The  end  k is  left  on  and 
serves  as  a handle  for  the  wrench  during  the  operation.  It 
runs  out  into  the  bar  of  greater  length  than  shown.  When 


§30 


DIES  AND  DIE  MAKING. 


35 


trimmed,  the  wrench  r falls  into  the  pocket  in  the  bottom 
of  the  die  and  is  pulled  out  through  the  slot  s.  The  end  k 


Fig.  32. 

is  finally  cut  off  on  a shear,  and  the  edges  finished  to 
the  form  shown  in  Fig.  32  ( b ) by  grinding  on  an  emery 
wheel. 


37.  Tube  Squirting. — A process  analogous  to  coin- 
ing, and  involving  the  same  principle  of  the  cold  flow  of 
metals,  is  the  pressing  of  small  disks  of  soft  metal,  such  as 
lead,  tin,  and  various  alloys,  into  the  thin  cylindrical  tubes 


C.  S.  111.— 43 


3G  DIES  AND  DIE  MAKING.  § 30 

used  for  holding  paints,  toilet  pastes,  etc.  In  Fig.  33  {a) 
is  shown  a pair  of  dies  for  this  purpose,  which,  it  will  be 

noticed,  are  very  simple.  At  ( b ) 
is  shown  a disk  of  metal,  punched 
out  in  another  machine,  and  at 
( c ) is  shown  the  tube  after  the 
pressure  has  caused  the  metal  to 
follow  the  shape  of  the  lower  die, 
including  the  hole  in  the  center 
and  the  threaded  neck.  The 
pressure  of  the  punch  causes  the 
surplus  metal  to  flow  up  the  sides 
of  the  punch  in  the  form  of  a 
thin  shell,  the  length  being  deter- 
mined by  the  amount  of  squeezing  that  is  performed  after 
it  commences  to  crowd  upwards.  Where  the  work  has  a 
thread  coined  on  it,  it  must  be  removed  from  the  die  by 
rotation  to  unscrew  it. 

If  the  lower  die  has  simply  a cylindrical  recess  and  the 
punch  a plain  solid  cylinder,  the  tube  would  of  course  be  a 
plain  shell  with  a flat  bottom,  the  thickness  of  the  latter 
depending  on  the  distance  the  punch  descended,  and  the 
thickness  of  the  walls  depending  on  the  amount  of  space  at 
each  side  between  the  punch  and  the  die.  In  such  case  the 
blank  (l?)  might  be  of  thinner  metal  than  shown  and  of 
larger  diameter,  as,  for  example,  the  diameter  of  the  outside 
of  the  tube. 


<a>  (b) 


FIG.  33. 


JIGS  AND  JIG  MAKING. 


JIGS. 


CLASSES  AND  USE  OF  JIGS. 


DEFINITIONS. 

1.  In  the  manufacture  of  duplicate  parts,  special  devices 
or  fixtures  are  largely  used  for  guiding  the  cutting  tools  in 
such  a manner  that  the  work  produced  by  them  becomes 
alike  in  all  essential  features,  independent  of  the  skill  of  the 
operator.  Such  devices  or  fixtures  are  commonly  called 
jigs;  they  are  used  chiefly  for  the  production  of  holes  of 
circular  cross-section  by  drilling  or  reaming  operations  or 
by  both  in  conjunction,  and  are  also  used  occasionally  for 
guiding  taps,  files,  or  other  tools. 

2.  Jigs  are  called  drill  jigs,  reaming  jigs,  tapping 
jigs,  or  filing  jigs,  or,  in  case  of  several  operations  of  dif- 
ferent kinds,  combination  jigs;  the  name  given  implies 
the  operation  in  the  performance  of  which  the  jig  is  intended 
to  aid.  The  design  of  jigs  for  any  of  these  operations  does 
not  differ  in  any  essential  particular;  hence,  whenever  the 
word  “jig”  is  used  hereafter,  it  will  be  understood  to  be 
applied  in  the  general  sense. 

§ 31 

For  notice  of  copyright,  see  page  immediately  following  the  title  page. 


2 


JIGS  AND  JIG  MAKING. 


§ 31 


ESSENTIAL  PARTS. 

3.  All  jigs  consist  of  certain  essential  parts,  which  are 
the  guides  for  the  cutting  tools;  the  body,  which  supports 
the  guides  and  the  work;  the  stops,  or  gauges,  which 
locate  the  work  correctly  in  reference  to  the  guides  and  to 
one  or  more  points  or  surfaces  of  the  work;  the  clamping 
arrangement,  which  serves  to  hold  the  work  to  the  body; 
and  the  supporting  surface  or  surfaces,  which  rest  on  the 
table  of  the  drill  press  and  insure  parallelism  of  the  axes  of 
the  guides  with  the  axis  of  the  spindle  that  carries  the  cut- 
ting tool. 

4*  The  clamping  arrangement  and  the  supporting  sur- 
face do  not  necessarily  form  an  integral  part  of  the  jig,  but 
may  be  separate  therefrom.  Thus,  in  some  cases,  the  jig 
and  the  work  may  be  held  together  by  C clamps  or  machin- 
ists’ clamps;  likewise,  the  supporting  surface  may  be  some 
suitable  part  of  the  work  itself.  In  all  cases,  however,  these 
two  features  must  exist  in  some  form,  and  the  plane  of  the 
supporting  surface  must  be  perpendicular  to  the  axis  of  the 
guide. 


TYPES  OF  JIGS. 

5.  Clamp  Jigs  and  Box  Jigs.  — There  are  two 
general  types  of  jigs  in  common  use,  each  of  which  has  its 
own  sphere  of  usefulness.  The  one  type  is  intended  for 
work  where  the  axes  of  all  holes  that  are  cut  by  the  aid  of 
the  jig  are  parallel.  The  holes  need  not  necessarily  be  loca- 
ted in  the  same  plane,  nor  must  they  be  drilled  from  the 
same  side  of  the  jig.  Since  jigs  of  this  type  frequently  re- 
semble some  form  of  a clamp,  they  are  by  common  consent 
termed  clamp  jigs,  although  in  some  cases  the  resemblance 
between  the  jig  and  a clamp  is  very  faint,  or  has  entirely 
disappeared.  The  other  type  of  jig  is  intended  for  work 
that  requires  the  holes  that  are  to  be  cut  through  it,  or  into 
it,  to  be  at  various  angles  to  one  another.  Since  jigs  of  this 
type  most  frequently  resemble  some  form  of  a box,  the  name 
of  box  jig  is  commonly  applied  to  any  jig  intended  for  holes 
at  angles  to  one  another. 


31 


JIGS  AND  JIG  MAKING. 


3 


GENERAL  REQUIREMENTS. 

G.  There  are  a number  of  general  requirements,  some 
or  all  of  which  must  be  partially  or  entirely  fulfilled  in  the 
design  and  construction  of  any  jig.  The  extent  to  which 
any  or  all  of  the  requirements  must  be  taken  into  considera- 
tion depends  on  circumstances;  each  particular  case  must  be 
decided  on  its  own  merits  with  special  reference  to  the  com- 
mercial feature.  Thus,  it  may  be  considered  as  the  height 
of  folly  to  make  a jig  worth  $50  to  do  a job  worth  $20  and 
which,  furthermore,  will  never  be  duplicated. 

7.  One  of  the  most  important  requirements  is  the  ease 
of  inserting  work  into  a jig  and  removing  it  from  the  jig. 
Evidently,  the  easier  this  necessary  operation  is  performed, 
the  more  work  can  be  turned  out  by  an  operator  when  all 
other  conditions  remain  the  same.  Ease  of  insertion  and 
removal  under  proper  management  means  reduction  of  the 
time  cost  per  piece. 

8.  A jig  should  be  so  constructed  that  it  can  easily  be 
cleaned,  especially  those  parts  of  it  that  act  as  stops  and 
locate  the  work  properly.  Chips  getting  between  the  work 
and  the  stops  will  throw  the  work  out  of  true,  and,  conse- 
quently, will  result  in  an  improper  location  of  the  holes. 
While  the  amount  may  not  be  very  large,  in  many  cases  it 
will  be  sufficient  to  spoil  the  work.  Now,  since  it  is  gener- 
ally agreed  that  the  most  stringent  orders  will  fail  to  make 
an  operator  clean  the  stops  of  a jig  properly  before  inserting 
a new  piece  of  work  when  a large  output  is  demanded,  it  is 
considered  best  to  make  the  stops  self-cleaning,  ,as  far  as  can 
be  done,  or  to  design  the  jig  so  that  it  can  be  cleaned  with 
a minimum  effort  and  preferably  without  any  special  appli- 
ances. 

9.  Interchangeability  of  the  work  depends,  in  a great 
measure,  on  proper  location  of  the  stops,  which  should  be  so 
arranged  as  to  give  an  invariable  location  of  the  work  in 
relation  to  the  guides  of  the  jig.  When  work  that  is  liable 
to  vary  slightly  in  its  dimensions  is  to  be  operated  upon  in 


4 JIGS  AND  JIG  MAKING.  § 31 

a jig,  the  stops  may  occasionally  have  to  be  made  adjustable 
in  order  to  accommodate  any  slight  variation  in  size  or 
shape. 

10.  Ease  of  clamping  the  work  to  the  jig,  or  vice  versa, 
is  a feature  that  may  profitably  be  studied  carefully  if  a 
large  number  of  pieces  are  required  to  be  made  in  the  jig. 
A rapid  clamping  arrangement  that  needs  little  muscular 
effort  is  conducive  to  a reduction  of  the  time  cost  per 
piece. 

11.  Clamping  arrangements  require  to  be  so  designed 
that  the  act  of  clamping  the  work  to  the  jig,  or  vice  versa, 
will  not  spring  the  work  or  the  jig.  If  either  is  sprung  out 
of  true  by  the  act  of  clamping,  inaccurate  work  will  natu- 
rally result. 

12.  Durability  of  a jig  is  a requirement  that  depends  on 
the  number  of  pieces  the  jig  is  to  be  used  for  as  to  the  extent 
to  which  it  is  to  be  fulfilled.  In  general,  only  such  dura- 
bility should  be  provided  as  will  serve  the  extent  of  service 
without  any  serious  loss  of  accuracy. 

13.  Adaptability  to  conversion  into  a combination  jig 
that  may  be  used  for  either  drilling,  reaming,  or  tapping  any 
or  all  the  holes  can  readily  be  secured  by  removable  guides 
of  sufficient  size,  so  arranged  as  to  always  center  themselves 
during  insertion.  Since  the  guides  almost  invariably  take 
the  form  of  hardened  concentric  steel  bushing,  this  is,  as  a 
general  rule,  a very  easy  matter. 

1 4.  Capability  of  accurate  duplication  is  of  prime  im- 
portance not  only  when  the  jig  is  in  constant  demand,  but 
also  when  a number  of  like  jigs  are  required.  In  the  first 
case,  the  natural  wear  and  the  unnatural  abuse  a jig  is  liable 
to  receive  will  sooner  or  later  call  for  its  duplication ; both  in 
the  first  and  in  the  second  case,  an  accurate  duplication  can, 
in  almost  all  instances,  be  readily  provided  for  by  making 
the  jig  or  jigs  either  from  a master  jig  preserved  for  this 
purpose,  or  from  templets  of  suitable  form  made  from  the 
first  jig  and  preserved. 


JIGS  AND  JIG  MAKING. 


5 


§ 31 


15.  Sufficient  extent  of  supporting  surface  will  prevent 
any  canting  of  the  jig  under  the  downward  pressure  of  drill- 
ing and  reaming,  and  will  thus  result  in  a reduction  of  the 
breakage  of  cutting  tools.  The  supporting  surface  need  not 
necessarily  be  an  unbroken  plane;  in  many  cases,  three  legs, 
which,  of  course,  will  give  a steady  support  in  spite  of  any 
slight  inequalities  of  the  drill-press  table,  are  greatly  pref- 
erable to  an  unbroken  surface.  In  other  cases,  four,  and 
even  more,  legs  whose  ends  lie  in  the  same  plane  may  prove 
of  advantage,  especially  when  the  distance  that  three  legs 
must  be  apart  in  order  to  prevent  canting  is  beyond  the 
range  of  the  drill  press  available.  In  order  that  the  jig  may 
not  tip  over  under  the  pressure  of  cutting  operations,  all 
guides  for  the  cutting  tools  must  lie  well  within  the  polygon 
that  is  formed  by  connecting  all  adjacent  points  of  support 
by  straight  lines. 

16.  Stiffness  is  not  only  desirable  for  most  jigs,  but  also 
becomes  essential  when  exact  duplication  of  the  work  is  re- 
quired. The  act  of  clamping  the  work  to  the  jig,  or  the  jig 
to  the  work,  with  many  designs  subjects  the  jig  to  bending 
stresses  that  tend  to  deform  it.  Since  these  bending  stresses 
cannot  be  expected  to  be  alike  each  time  the  jig  is  used,  it 
follows  that  the  amount  of  deformation  will  vary;  conse- 
quently, the  work  done  with  the  aid  of  the  jig  will  also  vary. 
Stiffness  may  best  be  obtained  by  properly  distributing  the 
metal  to  resist  such  bending  stresses  as  the  jig  may  be  sub- 
jected to;  the  proper  arrangement  of  supports  and  clamping 
arrangements  will  in  a measure  contribute  toward  stiffness. 

17.  Absence  of  sharp  corners  means  ease  of  handling; 
any  feature  that  makes  a tool  agreeable  to  the  touch  may 
confidently  be  expected  to  reduce  the  time  cost  per  piece. 

18.  Accuracy  of  the  jig  itself,  while  mentioned  last, 
is  the  most  important  requirement.  It  should  always  be 
remembered  that  any  inaccuracy  of  the  jig  will  be  dupli- 
cated in  the  work ; and  if  the  cutting  tools  are  loosely  guided, 
the  errors  may  enlarge.  While  accuracy  is  essential,  there 


6 


JIGS  AND  JIG  MAKING. 


31 


is  such  a thing  as  carrying  it  to  an  extreme.  The  toolmaker 
should  always  aim  to  obtain  the  accuracy  that  is  essential; 
any  further  reduction  means  a large  outlay  of  money  that  is 
generally  not  warranted  by  the  conditions  of  the  case. 


JIG  DETAILS. 


GUIDE  BUSHINGS. 

19.  Permanent  Bustlings. — The  guides  for  the  cut- 
ting tools,  which  are  usually  drills,  reamers,  or  taps,  most 
frequently  take  the  form  of  hardened  steel  bushings  set 
into  the  jig  body.  The  hole  in  the  bushing  is  made  to  fit 
the  drill,  reamer,  or  tap  shank  closely ; the  outside  of  the 
bushing  is  exactly  concentric  with  the  inside. 

20.  The  bushings  may  be  made  in  various  forms  to  suit 
different  purposes.  Common  forms  of  plain  bushings,  in- 
tended to  be  driven  into  suitable  holes  in  the 
jig  body,  are  shown  in  Figs.  1 and  2.  Refer- 
ring to  Fig.  1,  the  bushing  is  seen  to  be 
straight  inside  and  outside,  except  that  the 
end  where  the  drill  enters  is  rounded  out  to 
allow  it  to  enter  easily.  This  plain  bushing 
is  the  cheapest  bushing  to  make,  and,  if  well 

fitted  to  the  hole  that  receives  it,  is  thoroughly  satisfactory. 
The  only  objectionable  feature  is  that  when  a drill  too  large 
for  the  hole  is  forced  down  on  the  bushing,  it  is  liable  to 
push  the  bushing  through  its  seat.  This  is  very  liable 
to  happen  when  the  jig  is  used  on  a multiple-spindle  drill 
press. 

21.  In  order  to  prevent  the  bushing  from  being  pushed 
through  its  seat,  it  may  be  made  tapering  on  the  outside,  or 
it  may  be  allowed  to  project  from  the  seat.  The  projecting 
part  is  then  enlarged  to  form  a shoulder.  While  tapering 
the  outside  of  the  bushing  will  accomplish  the  object  to  be 
attained,  it  is  an  expensive  form  of  bushing  to  produce. 


JIGS  AND  JIG  MAKING. 


7 


§ 31 


Likewise,  it  is  expensive  to  bore  the  seat  for  it,  especially  if 
great  accuracy  in  the  location  of  its  axis  is  required.  On 
the  other  hand,  a tapered  bushing  is  easily  removed. 

22.  The  most  common  form  of  a straight  bushing  with 
an  enlarged  head  is  shown  in  Fig.  2 ( a ).  The  shoulder 


Fig.  2. 


under  the  head  is  made  square.  This  is  objectionable,  how- 
ever, for  two  reasons.  In  the  first  place,  in  hardening  the 
bushing,  a crack  is  liable  to  form  in  the  sharp  corner;  in  the 
second  place,  while  forcing  the  bushing  home  into  its  seat, 
the  head  is  rather  liable  to  be  broken  off.  The  end  that 
receives  the  drill  is  rounded  off  inside  and  out,  usually  semi- 
circular, as  shown. 

23.  A better  form  of  a straight  bushing  is  shown  in 
Fig.  2 ( b ).  Here  a liberal  sized  fillet  is  left  under  the  head, 
which  obviates  the  liability  of  cracking  in  hardening,  and 
reduces  the  liability  of  breaking  the  head  off  while  forcing 
the  bushing  home.  In  the  bushing  shown,  the  end  is 
rounded  out  considerably  more  on  the  inside  than  on  the 
outside;  this  makes  it  easier  for  the  drill  to  find  the  hole 
and  hence  is  preferable  to  the  semicircular  rounding  off 
shown  in  Fig.  2 ( a ).  When  the  bushing  is  to  be  ground  on 
the  outside  after  hardening,  it  is  advisable  to  very  slightly 
neck  it  down  under  the  shoulder  with  a round-nosed  tool; 
when  grinding  the  outside,  the  emery  wheel  can  then  pass 
clear  over  the  part  being  ground.  The  necking  down  is 
clearly  shown  in  Fig.  2 (c). 

24.  In  many  cases,  it  is  necessary  for  the  bushing  to 
project  some  distance  beyond  the  lower  part  of  its  seat,  in 


JIGS  AND  JIG  MAKING. 


§31 


order  that  the  point  of  the  drill  or  end  of  the  reamer  may 
be  supported  close  to  the  work.  In  that  case,  the  bushing 
may  take  the  form  shown  in  Fig.  2 ( d ).  As.  shown  in  the 
illustration,  it  is  counterbored  part  way  down,  in  order  to 
reduce  the  friction  of  the  drill  or  reamer  against  the  inner 
surface  of  the  bushing.  The  part  that  serves  to  guide  the 
cutting  tool  does  not,  in  general,  need  to  be  any  longer  than 
twice  its  diameter. 

The  bushings  so  far  shown  are  not  intended  to  be  removed 
except  for  the  purpose  of  renewal  when  worn. 

25.  Removable  Bushings. — Any  ordinary  jig  can 
readily  be  converted  into  a combination  jig  by  fitting  it 
with  two  or  more  sets  of  bushings.  One  set  may  then  be 
made  to  fit  the  drills;  the  second  set  may  be  made  to  guide 
the  reamers;  and  the  third  set  may  suit  the  tap  shanks. 
Obviously,  the  bushing  must  be  easily  removable.  There 
are  quite  a number  of  ways  in  which  this  may  be  done. 

2G.  The  simplest  way  is  to  make  a straight  bushing  a 
sliding  fit  in  its  seat  and  then  confine  it  by  a setscrew. 
While  this  can  be  done  advantageously  in  many  cases,  in 
others  the  location  of  the  bushing  prevents  the  use  of  a 
setscrew.  If  that  happens  to  be  the  case,  some  toolmakers 
will  fit  a tapered  bushing  to  a tapered  seat,  relying  on  the 
friction  to  hold  the  bushing  in  place  during  the  cutting 
operations. 

27.  Some  forms  of  a tapered  removable  bushing  are 
shown  in  Fig.  3.  The  simplest  form  is  shown  in  Fig.  3 (a) ; 


the  bushing  is  removed  by  driving  it  out  with  a drift  and  a 
hammer.  A better  form  is  shown  in  Fig.  3 (b).  Here  the 


(a) 


Fig.  3. 


JIGS  AND  JIG  MAKING. 


0 


31 


bashing  is  made  long  enough  to  project  beyond  its  seat;  its 
projecting  part  is  made  hexagonal  to  receive  a wrench,  by 
means  of  which  it  may  be  loosened.  In  order  that  the  time 
required  for  the  handling  of  the  wrench  may  be  saved,  the 
projecting  part  may  have  a handle  permanently  attached  to 
it,  'as  shown  in  Fig.  3 (< c ).  The  objection  to  this  last  form 

is  that,  in  many  cases,  the  handle  may  interfere  with  easy 
handling  of  the  jig. 


28.  Tapered  removable  bushings  are  not  only  open  to 
the  objection  that  they  are  expensive  to  produce,  but  also 
are  liable  to  be  thrown  out  of  their  true  location  by  any 
foreign  matter,  such  as  chips  or  waste,  getting  between  the 
outside  of  the  bushing  and  its  seat.  In  this  respect,  a 
straight  removable  bushing  will  have  the  advantage,  since 
it  will  push  all  foreign  matter  out  of  its  hole  during  inser- 
tion. On  the  other  hand,  in  the  case  of  the  tapered 
bushing,  wear  of  the  seat  will  not  affect  the  accurate  loca- 
tion of  the  bushings  to  an  appreciable  extent. 

29.  Removable  bushings  may  be  threaded  on  the 
outside,  and  may  be  provided  with  a hexagonal  head,  as 
shown  in  Fig.  4 (a).  The  seat  for  the  bushing  is  then 


(b) 


Fig.  4. 


chased  or  tapped  to  suit.  Since  the  bushing  is  very  liable 
to  change  its  shape  and  diameter  in  hardening,  a bushing 
that  is  threaded  should  be  finished  entirely  before  chasing 
the  thread  in  the  seat.  Obviously,  after  hardening,  it  is 
difficult  to  grind  the  thread  truly  concentric  with  the  hole; 
for  this  reason,  the  use  of  a bushing  of  the  form  shown  in 
Fig.  3 (a)  is  not  to  be  recommended  for  work  that  requires 
very  accurate  location  of  the  holes.  Furthermore,  the 


10 


JIGS  AND  JIG  MAKING. 


§ 31 


unevenness  of  the  thread  induced  by  the  hardening  process 
will  cause  a rapid  wear  of  the  thread  in  the  seat,  thus 
destroying  the  accurate  location. 

30.  A better  form  of  a threaded  bushing  is  shown  in 
Fig.  4 ( b ) and  (*;).  Here  the  thread  is  not  relied  on  to 
center  the  bushing  properly,  but  serves  merely  as  a con- 
venient means  of  attaching  and  detaching  it.  The  bushing 
is  centered  by  a cylindrical  part  that  closely  fits  a corre- 
sponding part  of  the  seat;  the  thread  is  made  a fairly  good 
fit  in  the  seat.  The  cylindrical  part  of  the  bushing  may  be 
either  below  or  above  the  threaded  part;  if  it  is  above,  the 
thread  in  the  seat  can  be  tapped  clear  through,  which  allows 
the  use  of  a plug  tap.  This  design  of  a threaded  bushing  is 
preferable  for  accurate  work,  since  the  cylindrical  part, 
after  hardening,  can  be  ground  true  with  the  hole.  While 
the  bushings  shown  in  Fig.  4 all  have  a hexagonal  head, 
they  may  be,  and  occasionally  are,  made  with  a large 
nurled  head,  and  also  with  a handle  similar  to  that  shown 
in  Fig.  3 (c). 

31.  Clamp  Bushings.  — A jig  bushing  may  serve  a 
double  purpose;  that  is,  it  may  be  used  for  guiding  the 
cutting  tool  and,  at  the  same  time,  for  clamping  the  work  to 


the  jig  body.  This  is  done  by  making  the  threaded  part  of 
the  bushing  long  enough  to  allow  the  end  to  be  screwed 
down  on  the  work.  There  are  many  cases  where  the  adop- 
tion of  one  or  more  clamp  bushings  will  allow  a very  simple 
design  of  a jig. 


Fig.  5. 


31 


JIGS  AND  JIG  MAKING. 


11 


32.  In  some  cases  where  the  work  has  cylindrical  pro- 
jections or  a recess,  a jig  bushing  may  be  made  to  act  as  a 
stop  for  centering  the  work  properly  and  clamping  it  at  the 
same  time.  Thus,  if  the  work  has  a cylindrical  or  conical 
recess,  the  lower  end  of  the  bushing  may  be  turned  conical, 
as  shown  in  Fig.  5 ( a ).  If  the  work  is  to  be  centered  by  a 
cylindrical  or  tapering  projection,  the  lower  end  of  the  bush- 
ing may  be  recessed  conical,  as  shown  in  Fig.  5 (5). 

33.  Size  of  Guide  Hole. — The  size  of  the  hole  in  the 
bushing  has  a very  important  influence  on  the  accuracy  with 
which  the  holes  are  drilled  into  the  work.  In  all  cases,  the 
drill  or  reamer  must  be  loose  enough  in  the  bushing  so  as 
not  to  bind  and  seize.  This  looseness  does  not  need  to  be 
much;  if  the  hole  is  .001  inch  larger  than  the  cutting  tool, 
there  is  little  danger  of  sticking.  How  much  the  hole  should 
be  made  larger  than  the  drill  would  be  easily  determined  if 
it  were  not  for  the  fact  that  the  commercial  sizes  of  the 
drills  do  not,  as  a general  rule,  agree  very  closely  with  their 
nominal  size.  While  the  variation  between  different  drills 
of  the  same  nominal  size  is  not  very  large,  and  not  sufficient 
to  be  appreciable  for  ordinary  work,  this  variation  becomes 
quite  appreciable  when  accurate  work  is  to  be  done  by  jig 
drilling. 

If  a number  of  drills  of  the  same  nominal  size  are  meas- 
ured, some  will  be  found  over  size,  some  under  size,  and,  per- 
haps, a few  correct  size.  The  toolmaker  now  has  the  choice 
of  several  methods  of  procedure.  He  may  make  the  guide 
hole  sufficiently  large  to  fit  the  largest  drill  in  the  lot,  which 
involves  a consequent  serious  looseness  of  fit  of  the  under- 
size drills;  or  he  may  make  the  guide  hole  standard  size  and 
stone  down  all  drills  that  are  over  size;  or,  further,  he  may 
make  the  bushing  to  suit  the  smallest  under-size  drill,  and 
stone  all  other  drills  down  to  suit  this  size. 

34.  Which  of  these  methods  is  to  be  adopted  is  purely  a 
question  of  the  accuracy  with  which  the  holes  are  to  be 
located,  and  the  accuracy  with  which  the  drilled  holes  are 
to  represent  their  nominal  size.  When  accuracy  of  location 


12 


JIGS  AND  JIG  MAKING. 


§31 


is  the  most  essential  factor,  the  third  method  is  preferable; 
if  keeping  the  holes  to  the  standard  size  is  deemed  most  im- 
portant, the  second  method  may  be  adopted;  and  for  a com- 
paratively rough  job,  the  first  method  may  be  chosen.  In 
choosing  a method,  it  is  to  be  observed  that  great  accuracy, 
in  regard  to  keeping  all  holes  drilled  with  the  aid  of  the  jig 
to  the  same  size,  must  not  be  expected  by  drilling;  as  well 
known,  a drill  can  drill  a hole  considerably  larger  than  itself 
if  it  is  ground  so  that  its  point  is  out  of  center. 

35.  Material  for  Bushings. — The  material  to-  be 
chosen  for  making  the  bushings  depends  on  the  resistance 
to  wear  that  is  deemed  essential.  Hardened  tool-steel  bush- 
ings left  as  hard  as  fire  and  water  can  make  them  will  resist 
wear  better  than  machinery-steel  bushings  that  have  been 
case-hardened  with  cyanide  or  prussiate  of  potassium. 
Machinery  steel  will  answer  very  well  for  bushings  that  are 
intended  for  temporary  jigs;  if  the  jig  is  in  constant  use, 
however,  it  is  usually  advisable  to  choose  tool  steel  and 
harden  the  bushings. 

36.  Grinding  Bushings. — Since  the  hardening  proc- 
ess not  only  changes  the  size  but  also  the  shape  of  the 
bushings,  they  should  be  ground  both  inside  and  outside 
after  hardening,  if  great  accuracy  in  the  central  location  of 
the  guide  holes  in  reference  to  the  seat  is  deemed  essential. 
In  many  cases,  however,  dependence  can  be  placed  on  the 
fact  that  forcing  the  bushing  home  will  partially  correct  any 
deviation  from  roundness  induced  by  hardening,  especially 
if  the  walls  of  the  bushings  are  thin.  In  that  case,  the 
bushings  may  be  lapped  to  size  after  they  have  been  forced 
home. 


CLAMPING  DEVICES. 

37.  Jigs  are  supplied  with  clamping  devices  of  vari- 
ous forms  for  one  or  both  of  two  different  purposes:  to 
clamp  the  work  to  the  jig  body  or  to  clamp  some  part  of  the 
jig  made  movable  to  provide  for  inserting  and  removing 
work. 


§31 


JIGS  AND  JIG  MAKING. 


13 


38.  Clamps  intended  for  the  purpose  first  mentioned 
may  be  designed  in  various  ways  to  suit  different  conditions. 
For  some  work  the  hook  bolt  shown 
in  Fig.  6 is  very  well  adapted,  being 
cheap  in  construction  and  easily  ap- 
plied. The  bolt  proper  passes  through 
a hole  in  the  jig,  which  it  fits  closely. 

It  is  made  long  enough  to  have  the 
head  hook  over  some  projecting  part 
of  the  work,  and  may  be  supplied 
with  a wing  nut  as  shown,  or  have 
an  ordinary  hexagonal  nut.  In  some  cases,  a large  nurled 
nut  may  be  of  advantage.  The  greatest  clamping  pressure 
can  be  obtained  with  a hexagonal  nut  and  a wrench;  a mod- 
erate pressure  can  be  obtained  with  the  wing  nut  or  the 
nurled  nut.  However,  the  wing  nut  or  nurled  nut  allows 
the  hook  bolt  to  be  applied  more  rapidly.  It  will  be  under- 
stood that  in  order  to  allow  the  work  to  be  inserted  or 
removed,  the  loosened  hook  bolt  is  turned  so  that  its  head 
is  away  from  the  work;  when  the  work  has  been  inserted, 
the  head  is  turned  toward  the  work  and  hooks  over  it.  The 
clamping  is  then  done  by  screwing  up  the  nut. 


39.  In  jigs  that  partially  or  entirely  surround  the  work, 
it  is  most  commonly  held  in  place  by  setscrews,  which  may 
be  designed  in  several  ways.  When 
drop-forged  thumbscrews  are  avail- 
able, they  are  generally  used,  since 
comparatively  little  work  is  required 
to  finish  them.  When  these  cannot 
be  obtained,  the  setscrews  may  be 
made  as  shown  in  Fig.  7 by  driving  a 
cylindrical  pin  into  a hole  drilled 
through  the  head  of  the  screw.  In 
many  cases,  the  ordinary  setscrews 
that  can  be  bought  in  the  market  may  be  used.  These, 
however,  require  a wrench  for  tightening,  and  hence  are  not 
so  readily  used  as  thumbscrews,  or  the  screw  illustrated  in 
Fig.  7. 


Fig. 


14 


JIGS  AND  JIG  MAKING. 


31 


40.  Fig.  8 shows  a common  clamping  arrangement  for 
locking  two  parts  of  a jig  together.  The  thumbscrew  shown 


Fig.  8. 

is  screwed  into  a tapped  hole  in  the  jig  body,  as  a.  The 
shank  passes  through  a slot  b'  in  the  movable  part  b of  the 
jig.  This  slot  is  wide  and  long  enough  to  allow  the  head  to 
clear  it  when  the  screw  has  been  given  a quarter-turn  from 
the  position  shown.  Evidently,  this  is  a very  rapid  clamp- 
ing arrangement.  The  only  objection  is  that,  as  the  threads 
and  the  bearing  surfaces  wear,  the  head  will  finally  come  in 
line  with  the  slot  in  the  movable  part. 

41.  Fig.  9 shows  a hinged  bolt,  which  is  hinged  to  the 
stationary  part  a of  the  jig  by  means  of  the  pin  shown.  The 


bolt  passes  through  a slot  in  the  movable  part  b , open  on  one 
end,  and  is  provided  with  a nut  and  washer.  The  nut  may 


JIGS  AND  JIG  MAKING. 


15 


§ 31 


be  a wing  nut,  as  shown,  or  a hexagonal  or  nurled  nut. 
Wear  of  the  bearing  surface  or  of  the  pin  joint  does  not 
affect  the  clamping.  As  the  nut  must  be  unscrewed  some 
distance  to  allow  the  bolt  to  be  swung  clear  of  the  slot,  this 
arrangement  is  not  quite  so  rapid  as  that  shown  in  Fig.  8. 

42.  Fig.  10  shows  a hinged  cam-lever  pivoted  to  the  sta- 
tionary part  a of  the  jig.  Its  shank  passes  into  a slot  in  the 


movable  part  b\  the  bearing  surfaces  of  the  head  engage 
inclined  surfaces  of  the  movable  part.  Where  extreme  ra- 
pidity of  clamping  is  desired,  this  design  can  be  recommended. 


STOP-PINS. 

43.  I n order  to  prevent  any  shifting  of  the  work  in  the 
jig  during  the  cutting  operations,  one  or  more  stop-pins 
may  be  provided.  These  are  usually  made  cylindrical,  and 
are  closely  fitted  to  the  guide  bushing.  They  should  be 
provided  with  a suitable  handle  to  facilitate  withdrawal. 
To  prevent  shifting  of  the  work,  a stop-pin  is  pushed  through 
the  bushing  into  the  hole  in  the  work  as  soon  as  the  hole  has 
been  drilled.  Since  the  work  must  be  confined  at  least  in 
two  places  to  surely  prevent  any  liability  of  shifting,  two 
stop-pins  are  often  provided.  It  is  a good  idea  always  to 
select  the  holes  that  are  the  farthest  apart  for  the  stop-pins. 

C.  S ..  111.— 43a 


16 


JIGS  AND  JIG  MAKING. 


§31 


JIG  MAKING. 


EXAMPLES  OF  JIG  DESIGN. 

44.  Owing  to  the  innumerable  shapes  that  the  work  a 
jig  is  intended  for  may  have,  no  specific  directions  can  'be 
given  as  to  the  design  of  a jig.  The  general  requirements 
previously  given  should  in  each  case  be  fulfilled  to  the  extent 
that  the  circumstances  render  advisable.  The  designs  given 
here  will  serve  as  suggestions  to  the  toolmaker,  but  they 
must  be  modified  to  suit  conditions  and  requirements. 


45.  The  simplest  form  of  a jig  is  shown  in  Fig.  11.  The 

jig  simply  consists  of  a flat 
plate  made  of  suitable  ma- 
terial. The  outline  of  the 
jig  is  the  same  as  that  of 
the  work;  holes  are  drilled 
in  the  jig  to  serve  as  guides. 
The  jig  is  intended  to  be 
laid  on  the  work  and  is  then 
clamped  to  it  by  any  suit* 
able  and  convenient  means 


o 

NS  45  Drill. 

G 

N2  45  Drill. 

o 

N?  50  Drill. 

Fig.  ii. 


so  that  its  outline  coincides  with  that  of  the  work. 


46.  Such  a jig  is  cheap,  and  will  serve  well  for  flat 
work  where  extreme  accuracy  in  the  location  of  the  holes  is 
not  essential.  For  small  work  it  will  last  quite  well  if  made 
of  sheet  tool  steel  and  hardened  all  over.  When  it  is  to 
be  used  for  a small  number  of  pieces,  it  may  be  made  of 
machinery  steel  and  the  holes  case-hardened.  When  the 
holes  wear,  either  a new  jig  must  be  made  or  the  holes 
counterbored  to  receive  hardened  steel  bushings. 

47.  In  the  latter  case,  the  jig  takes  the  form  shown  in 
Fig.  12,  which  may  be  considered  as  the  second  step  in  the 
development  of  a jig.  Since  the  bushings  can  be  replaced 
easily  when  worn,  the  center-to-center  distance  of  their  axes 
can  be  accurately  preserved.  Beyond  this  fact,  the  design 


§31 


JIGS  AND  JIG  MAKING. 


17 


shown  is  not  particularly  more  advantageous  than  the  one 
shown  in  Fig.  11,  ex- 
cept that  it  may  be 
used  for  sizes  that 
would  prevent  heating 
and  hardening  the  en- 
tire jig. 

48.  Fig.  13  illus- 
trates a more  advanced 
form,  in  which  stops 
have  been  added  for 
the  purpose  of  alining 
the  jig  on  the  work.  In  this  particular  instance,  the  stops 
are  formed  by  flanges  a,  a and  pins  b , so  placed  as  to  suit 

the  outline  of  the  work.  If  the  different  pieces  of  work  are 
quite  uniform,  as,  for  instance,  if  the  outline  has  been  fin- 
ished by  profiling,  punching,  or  milling,  quite  accurate  work 


fig.  13. 

can  be  done  in  a jig  of  this  design.  In  many  instances,  it 
is  not  even  necessary  to  clamp  the  work  to  the  jig,  as  the 
stops  will  often  be  sufficient  to  prevent  shifting  of  the  jig. 


49.  A further  development  of  a jig  is  shown  in  Fig.  14, 
where  a clamping  attachment  has  been  added.  The  jig  is 
here  made  in  two  parts,  hinged  together  at  one  end.  The 


18  JIGS  AND  JIG  MAKING.  § 31 

pressure  of  the  hand  of  the  operator  is  intended  to  clamp 


Fig.  14. 


the  work  to  the  jig;  stop-pins  placed  to  suit  the  outline  of 
the  work  insure  an  unvarying  location  of  the  holes  in  refer- 


ence to  the  outline.  A jig  of  this  kind  is  well  adapted  for 
drilling  holes  through  small  flat  work  of  uniform  thickness. 


JIGS  AND  JIG  MAKING. 


19 


g 31 


50.  Fig.  15  shows  a jig  design  well  adapted  for  drilling 
holes  through  flanges.  The  jig  body  is  recessed  to  go  over 
the  flange,  and  the  jig  is  attached  and  clamped  by  means 
of  the  hook  bolts  shown.  Attention  is  called  to  the  position 
of  the  hook  bolts  in  reference  to  the  bushings.  They  should 
always  be  so  located  that  neither  the  head  of  the  hook  bolt 
nor  the  nut  can  ever  come  in  the  way  of  the  drill,  reamer, 
or  tap  that  is  intended  to  be  guided  by  the  bushing.  Jigs  of 
this  design  are  readily  modified  to  be  alined  to  a bored  or 
cored  hole  in  the  work  by  providing  the  lower  surface  with 
a projection  of  suitable  shape  instead  of  the  recess  shown. 


51.  With  the  exception  of  the  jig  illustrated  in  Fig.  14, 
all  the  designs  thus  far  shown  depend  on  the  work  itself  for 
furnishing  a supporting  surface  to  sustain  the  downward 
thrust  of  the  cutting  operations.  Fig.  16  shows  a jig  in 


which  the  work  is  placed  within  the  jig,  and  where,  conse- 
quently, the  thrust  is  taken  by  a suitable  surface  of  the  jig. 
Referring  to  the  illustration,  it  is  seen  that  the  jig  is  made 
of  two  parts  for  the  sake  of  convenience  in  machining  it. 
The  cover  a is  fastened  by  the  screws  shown;  an  invariable 
location  of  the  bushings  in  reference  to  the  stops  is  insured 


20 


JIGS  AND  JIG  MAKING.  § 31 


by  dowel  pins  b,  b.  This  precaution  is  necessary  when  the 
stops  are  contained  in  a part  of  the  jig  that  is  separate  from 
that  which  carries  the  bushings.  The  work  is  pushed 
against  the  stops  by  the  setscrews  c and  c' ; it  is  held  down 
by  the  setscrew  d.  In  this  case,  the  surface  e of  the  jig  has 
been  selected  as  a suitable  stop  to  gauge  the  location  of  the 
work  sidewise;  its  longitudinal  location  is  gauged  by  the 
stop-pin  f.  It  will  be  observed  that  the  setscrew  c is  placed 
at  an  angle  with  c' . Owing  to  the  way  in  which  it  bears 
against  the  work,  the  tightening  up  of  the  setscrew  will  not 
only  push  the  work  against  both  stops,  but  will  also  prevent 
any  longitudinal  movement,  thus  doing  away  with  the 
necessity  of  placing  another  setscrew  at  the  right-hand  end 
of  the  jig. 

The  design  shown  possesses  several  disadvantages.  In 
the  first  place,  it  is  rather  difficult  to  clean  it  properly;  in 
the  second  place,  it  is  easy  to  spring  the  work  out  of  true 
with  the  setscrew  d. 


b b 


Fig.  17. 


52.  Fig.  17  shows  how  a jig  may  be  made  for  the  same 
piece  that  the  design  shown  in  Fig.  1G  was  intended  for,  in 


§31 


JIGS  AND  JIG  MAKING. 


21 


order  to  overcome  the  objectionable  features  of  that  design. 
The  jig  body  a is  composed  of  one  piece  in  this  instance, 
which  is  open  in  front  to  allow  easy  insertion  and  removal 
of  the  work,  and  to  make  the  jig  accessible  for  cleaning.  In 
order  to  do  away  with  clamping  screws  and  stops,  the  bush- 
ings b,  b themselves  are  made  to  act  as  such.  This  makes 
a very  simple  and  cheaply  made  jig,  well  adapted  for  work 
like  that  shown  clamped  in  the  jig. 


Fig.  18. 


53.  Ease  of  insertion  and  removal  and  accessibility  for 
cleaning  may  often  be  secured  by  making  some  part  of  the 
jig  movable.  Thus,  in  Fig.  18,  the  top  part  a of  the  jig  is 


22 


JIGS  AND  JIG  MAKING. 


§ 31 


Fig.  19. 


JIGS  AND  JIG  MAKING. 


23 


§ 31 


hinged  to  the  body  b;  the  two  parts  are  clamped  together 
by  the  hinged  bolt  c.  In  order  to  show  the  slot  in  a clearly, 
the  wing  nut  and  washer  of  this  bolt  are  shown  removed  in 
the  plan  view.  The  work  is  supported  against  the  thrust  of 
the  cutting  operation  by  clamping  bushings  d,  d ’,  the  ends 
of  which  are  chamfered  in  order  to  act  as  stops  at  the  same 
time.  The  guide  bushings  e%  e in  this  case  have  a shoulder 
on  their  lower  end  for  the  purpose  of  preventing  the  upward 
pressure  of  the-  clamping  bushings  from  moving  them. 
Three  legs/",  /"are  fastened  to  the  jig  body;  these  legs  rest 
on  the  drill-press  table  while  the  jig  is  in  use.  They  must 
be  made  long  enough  to  insure  that  the  lower  end  of  the 
clamping  bushings  will  always  come  clear  of  the  table. 

The  design  is  shown  applied  to  work  in  which  the  holes 
do  not  lie  in  the  same  horizontal  plane;  it  may  be  applied  to 
other  work,  however.  Every  part  of  the  jig  is  accessible ; 
the  work  is  automatically  centered  and  the  disadvantages 
of  threaded  guide  bushings  are  avoided.  The  liability  of 
springing  the  jig  in  the  clamping  operation  is  greatly  re- 
duced by  providing  the  clamping  bushings  with  nurled 
heads  on  which  the  fingers  of  the  operator  will  slip  before 
he  can  tighten  them  sufficiently  to  spring  the  jig  out  of 
true. 


54.  Fig.  19  shows  a form  of  jig  that  is  largely  used  for 
drilling  holes  in  the  flanges  of  work  that  has  a cross-section 
similar  to  that  shown  in  the  illustration,  where  a represents 
the  work.  Since  three  legs  would,  in  this  case,  make  the 
jig  rather  complicated,  four  are  used.  The  jig  body  b is 
simply  a flat  plate  into  which  four  legs  are  screwed.  Two 
opposite  legs  are  slotted  to  receive  the  yoke  c , which  is 
hinged  at  one  end,  and  secured  in  position  at  the  other  end 
by  a removable  pin  d.  This  yoke  carries  the  setscrew  e , by 
means  of  which  the  work  is  clamped  to  the  jig.  When  the 
work  has  a hole  in  line  with  the  setscrew,  the  latter  may 
terminate  in  a circular  plate,  as  e' . To  insert  or  remove 
the  work,  the  jig  is  turned  upside  down;  the  pin  d is  then 
removed  and  the  yoke  swung  out  of  the  way.  When  the 


24 


JIGS  AND  JIG  MAKING. 


31 


Fig.  20. 


JIGS  AND  JIG  MAKING. 


25 


§ 31 


jig  is  used  for  castings,  which,  as  well  known,  are  bound  to 
vary  slightly  in  size,  the  jig  may  be  provided  with  a self- 
centering arrangement. 

Referring  to  the  figure,  f is  a plate  that  can  be  rotated 
by  means  of  the  handle  g.  This  plate  carries  three  pins  z,  i 
that  enter  slots  formed  in  the  jaws  /z,  h . These  jaws  are 
pivoted  to  the  jig  body  by  screws,  as  k , k , and  their  axes  are 
placed  nearer  .the  axis  of  rotation  of  the  plate  f than  the 
pins  z,  z.  In  consequence  of  this,  a right-handed  rotation 
of  the  plate  will  cause  the  jaws  to  swing  around  their  ful- 
crum screws  until  they  come  against  the  work,  which  is 
thus  centered.  The  design  of  centering  arrangement  is  not 
given  as  the  best  one  that  could  be  devised,  but  simply 
shows  one  way  of  accomplishing  the  object  to  be  attained. 


55.  All  the  jigs  so  far  shown  are  intended  for  drill- 
ing work  ip  which  the  axes  of  all  holes  are  parallel.  Fig.  20 
shows  a jig  designed  for  drilling  holes  in  three  different  direc- 
tions in  one  chucking.  Referring  to  Fig.  20,  the  work  a , 
which  is  shown  in  perspective  in  Fig.  20  ( a ),  is  to  be  pierced 
by  the  holes  c,  d<  and  <?,  and  is  to  have  the  blind  hole  f 
drilled  to  a clearance  and  tapping  size.  This  hole  f is  re- 
cessed, as  shown,  in  a separate  operation.  In  the  work 
shown,  it  is  essential  that  the  holes  should  be  located  cor- 
rectly in  reference  to  the  two  surfaces  in  contact  with  the 
stops  of  the  jig  body. 

To  allow  the  work  to  be  easily  inserted  and  removed  and 
to  give  accessibility,  the  jig  is  made  in  two  parts,  of  which 
the  part  g carries  all  the  bushings,  stops,  and  the  legs  that 
form  the  supporting  surfaces.  For  drilling  the  hole  //,  the 
jig  is  supported  on  the  three  legs  h , /z,  /z,  the  plane  of  which  is 
perpendicular  to  the  axis  of  d.  For  drilling  the  holes  b , r, 
and  <?,  the  jig  is  supported  on  the  legs  z,  z,  z.  Three  points  of 
support,  as  k , k,  k , are  provided  for  drilling  the  hole  f.  An 
examination  of  the  shape  of  the  work  shows  that  it  can  be 
held  against  the  stops  in  two  directions  by  a setscrew  placed 
as  /;  it  is  held  against  the  surface  g'  by  the  setscrew  mn 
which  is  located  in  the  movable  hinged  part  n of  the  jig. 


26 


JIGS  AND  JIG  MAKING. 


§31 


The  part  n is  clamped  by  the  clamp  screw  o.  The  guide 
bushings  for  drilling  the  holes  b , c , d , r,  and  f are  shown  at 
b\  c\  d' , e\  and respectively.  As  far  as  the  holes  d and  f 
are  concerned,  the  holes  have  two  sizes  each.  The  bush- 
ings for  them  are  made  to  the  larger  sizes,  and  drilling  is 
continued  with  smaller  drills  after  the  holes  have  been  drilled 
their  large  size  to  the  correct  depth.  The  bushing  f'  is 
pierced  by  a clearance  hole;  since  this  hole  penetrates  above 
the  guiding  part  of  the  bushing,  there  is  no  particular  objec- 
tion to  piercing  the  bushing.  Clearance  holes  as  blt  cv 
and  ex  are  drilled  through  the  movable  cover  in  line  with  the 
bushings  for  the  escape  of  chips. 


LOCATING  HOLES. 


LOCATING  HOLES  FROM  A DRAWING. 

56.  The  problem  of  correctly  locating  the  holes  that 
receive  the  guide  bushings  presents  itself  usually  in  one  of 
two  different  ways.  Either  the  holes  are  to  be  laid  out  from 
a dimensioned  drawing  or  they  are  to  be  transferred  from  a 
model  of  the  work.  The  choice  of  method  of  procedure  de- 
pends on  the  accuracy  required  and  also  on  other  conditions, 
such  as  the  facilities  at  hand  and  the  nature  of  the  work. 

57.  When  extreme  accuracy  is  not  required,  the  centers 
of  the  holes  are  laid  out  in  the  same  manner  in  which  the 
machinist  lays  out  his  work,  that  is,  by  scribing  lines  with 
scriber,  surface  gauge,  etc.  In  that  case,  all  dimensions  are 
transferred  from  a steel  rule.  Since  the  intersections  of 
the  scribed  lines  represent  the  centers  of  the  holes,  they  are 
carefully  marked  by  a fine  prick-punch  mark  and  a witness 
circle  slightly  larger  than  the  proposed  hole  is  drawn  from 
each  prick-punch  mark  as  a center.  There  is  now  the  choice 
of  two  methods  for  putting  the  hole  through  the  jig.  The 
holes  may  be  drilled  and  reamed  in  the  drill  press,  or  they 
may  be  bored  in  the  lathe.  Drilling  and  reaming  the  holes 
in  the  drill  press  has  the  advantage  of  cheapness,  but  will 


§31 


JIGS  AND  JIG  MAKING. 


27 


insure  only  a fair  degree  of  accuracy  in  the  location  of  the 
holes,  since  any  lack  of  homogeneity  in  the  metal  will  cause 
the  drill  to  run  to  one  side  or  the  other.  With  reasonable  care 
in  laying  out  the  holes,  and  in  the  subsequent  drilling  and 
reaming,  the  holes,  as  a general  rule,  may  be  located  within 
a limit  of  variation  of  .005  inch.  If  extreme  care  is  used, 
the  holes  may  be  located  within  .003  inch;  this  may  be  con- 
sidered as  the  limit  of  accuracy  attainable  by  this  method. 

58.  The  relatively  low  degree  of  accuracy  attainable  by 
the  use  of  the  method  just  given  is  due  to  the  existence  of 
two  errors,  neither  of  which  can  be  eliminated  entirely  by 
design,  although,  as  the  result  of  accident,  either  or  both 
may  occasionally  be  so  small  as  to  be  insensible.  One  of 
these  errors  is  that  due  to  an  accumulation  of  the  individual 
errors  of  each  successive  stage  of  the  laying-out  process; 
this  accumulation  of  errors  finally  appears  as  a lateral  devia- 
tion of  the  axis  of  the  prick-punch  mark  from  the  true  loca- 
tion of  the  axis  intended  to  be  represented  by  it.  The  second 
error  is  due  to  running  out  of  the  drill,  which  is  caused  by 
lack  of  homogeneity  of  the  metal  or  by  carelessness,  and, 
frequently,  by  a combination  of  both.  Either  error  can  be 
minimized  by  careful  work;  the  extent  to  which  it  can  be 
minimized  is  a quantity  whose  relative  value  depends  entirely 
on  the  skill  of  the  toolmaker. 

59.  In  order  to  reduce  the  limit  of  variation,  a modifi- 
cation of  the  method  previously  given  may  be  employed. 
This  modification  will  neither  reduce  nor  eliminate  the  error 
of  laying  out,  but  will  greatly  reduce  the  error  of  putting 
the  hole  through  the  jig.  In  addition,  it  will  insure  that  the 
axis  of  the  hole  is  perpendicular  to  the  supporting  surface. 
After  laying  the  holes  out  properly,  the  jig  is  strapped 
against  a true-running  straight  face  plate  and  is  trued  up 
successively  to  the  various  prick-punch  marks  by  means  of 
a sensitive  center  indicator.  After  each  truing  up,  a hole 
is  drilled  clear  through;  the  hole  is  then  finished  by  careful 
boring  with  a sharp  tool.  In  order  to  do  accurate  work,  it 


28  JIGS  AND  JIG-  MAKING.  § 31 

is  necessary  to  counterbalance  the  weight  of  the  jig  by  attach- 
ing a suitable  weight  to  the  face  plate,  and  opposite  the  jig. 
The  boxes  in  which  the  lathe  spindle  runs  must  be  set  quite 
close,  and  all  end  movement  of  the  lathe  spindle  should  be 
taken  up.  Also  examine  the  belt  lacing;  if  this  shows  a 
decided  lump,  relace  the  belt  smoothly.  Otherwise,  every 
time  the  lacing  strikes  the  cone  of  the  live  spindle  it  will 
cause  the  latter  to  jump  to  the  extent  of  the  looseness 
between  the  spindle  and  its  boxes. 

With  extremely  careful  work  in  laying  out,  truing  up, 
and  boring,  the  holes  may  be  located  within  a limit  of  varia- 
tion as  small  as  .0015  inch.  The  method  given  is  limited  in 
its  application  by  the  swing  of  the  largest  lathe  available. 

60.  If  the  holes  in  the  jig  are  to  be  located  closer  than 
is  usually  possible  by  the  method  given  in  Art.  59,  contact 
measurements,  as  far  as  practicable,  must  be  substituted 
for  measurements  transferred  by  scribed  lines.  The  tools 
required  are  a micrometer  caliper  of  sufficient  capacity  or  a 
measuring  machine,  and  a number  of  annular  circular  steel 
buttons.  These  buttons  may  be  of  any  convenient  size;  a 
good  size  is  \ inch  outside  diameter,  ^ inch  inside  diameter, 
and  J inch  thick.  They  are  attached  to  the  work  by  means 
of  fillister-headed  screws  of  about  T3g-  inch  diameter;  No. 
10-32  machine  screws  will  be  found  very  convenient  for  this 
purpose.  The  buttons  should  be  made  of  tool  steel  and 
they  should  be  ground  truly  circular  after  hardening. 

61.  The  method  of  using  the  buttons  for  a case  where 

all  holes  are  to  be  in  the 
same  plane  is  perhaps 
best  shown  by  a concrete 
example.  Let  Fig.  21  be 
a working  drawing  of 
part  of  a jig  in  which 
the  holes  a and  b are  to 
be  located  with  reference 
to  each  other  and  to  the 
surfaces  c and  d within 


Scale  Ma.lf  Sh 


JIGS  AND  JIG  MAKING. 


29 


§ 31 


as  small  a limit  of  variation  as  possible.  The  position  of  the 
holes  is  first  laid  out  by  scribing  lines  with  the  aid  of  a surface 
gauge  or  scribing  block,  as  e in  Fig.  22,  setting  the  point  of 
the  scriber  f to  a steel  scale  resting  on  the  surface  plate  and 


Fig.  22. 


means  of  the  screws. 


held  upright  by  being  placed  against  a square,  as  shown. 
For  convenience,  the  scale  may  be  secured  to  the  square  by 
one  or  two  rubber  bands.  The  centers  of  the  holes  having 
been  laid  out,  they  are  center-punched  and  then  drilled  and 
tapped  for  the  size  of  machine  screw  chosen. 

The  buttons,  as  a'  and  b'  in  Fig.  23,  are  now  attached  by 
Since  the  hole  in  the  button  is  larger 
than  the  diameter  of  the  screw,  it  fol- 
lows that  the  buttons  can  be  shifted  a 
limited  amount.  Assume  that  the  but- 
tons are  both  .5  inch  diameter.  Then, 
to  place  the  button  a'  at  a distance  of 
1 inch  (see  Fig.  21)  from  d , first  make 
a gauge,  as  Fig.  23,  equal  in  length 
to  the  difference  between  the  radius  of 

5 

a'  and  the  given  dimension,  or  1 - - 

z 


IG  ■ = .75  inch  long.  Then,  shift  the  but- 

ton until  the  gauge  e,  when  perpendicular  to  d , will  just 
touch  d and  a'  with  the  same  degree  of  tightness  with  which 
it  fits  the  micrometer. 

To  locate  the  axis  of  a'  in  reference  to  c , the  jig  may  be 


30  JIGS  AND  JIG  MAKING.  § 31 

placed  on  a surface  plate  with  the  surface  c resting  on  the 
plate.  Then,  in  a manner  similar  to  that  employed  to  locate 
the  button  in  reference  to  d , it  may  be  located  at  the  proper 
distance  from  c.  The  screw  may  now  be  tightened  and  the 
proper  adjustment  of  the  button  tested  again,  since  the 
tightening  process  is  liable  to  shift  it. 

The  location  of  b'  in  respect  to  d is  simply  a repetition  of 
the  method  employed  to  locate  a' . When  we  come  to 
locate  it  in  reference  to  the  button  a\  two  ways  may  be 
employed.  We  may  obtain  the  center-to-center  distance 
between  a!  and  b ’ by  trigonometrical  calculation,  subtract 
the  sum  of  the  radii  of  the  two  buttons  from  it  and  file  a 
wire,  as  ff  Fig.  23,  to  it,  and  use  this  wire  to  aline  br.  If 
this  is  not  feasible  or  desirable,  the  button  b'  may  be  located 
from  the  surface  c in  the  same  manner  that  a ' was  located 
in  reference  to  that  surface.  After  locating  b\  it  is  clamped 
tightly  to  the  piece  and  then  tested  again.  If  found  cor- 
rect, the  piece  may  now  be  strapped  to  the  face  plate  of  a 
lathe  and  trued  up  by  shifting  until  one  of  the  buttons  runs 
true  ; that  is,  until  its  axis  coincides  with  the  axis  of  the 
lathe  spindle.  An  indicator  is  indispensable  for  this. 

It  may  be  well  to  call  attention  to  the  fact  that,  in  order 
to  do  any  accurate  work,  the  lathe  spindle  must  be  truly 
cylindrical  and  must  fit  the  boxes  very  closely.  The  face 
plate  should  also  be  counterbalanced  and  the  belt  lacing 
properly  fixed.  After  truing  up,  the  button  may  be  re- 
moved and  the  hole  bored  to  the  required  size.  The  other 
hole  is  similarly  treated. 

62.  When  the  guide  bushings  do  not  lie  in  the  same 
horizontal  plane,  as,  for  instance,  when  a jig  having  the 
cross-section  shown  in  Fig.  24  is  to  receive  guide  bushings 
in  the  places  indicated  by  the  dotted  lines  at  a and  b,  re- 
spectively, it  is  evident  that  no  direct-contact  measurement 
between  the  buttons  is  feasible  if  they  are  attached  to  the 
top  and  flange  of  the  jig.  In  such  a case,  a temporary  flat 
plate,  as  c , may  be  attached  and  the  buttons  may  then  be 
fastened  to  this  plate  in  order  to  bring  them  all  into  the 


§31 


JIGS  AND  JIG  MAKING. 


31 


same  plane.  This  plate  must  be  straight  and  parallel,  and 
so  fastened  as  to  preclude  any  possibility  of  shifting.  After 
boring  all  holes  through  plate  and  jig,  this  plate  may  be 
saved;  it  will  be  of  great  value  in  duplicating  the  jig.  To 
duplicate  the  jig,  the  plate  is  then  fastened  in  the  same 


relative  position  it  occupied  on  the  jig  first  made;  the  jig  is 
next  trued  up  by  the  holes  in  the  plate,  using  an  indica- 
tor for  the  purpose  of  obtaining  accuracy,  and  the  holes  are 
bored. 


LOCATING  HOLES  FROM  A MODEL. 

63.  When  a jig  is  to  be  made  to  suit  the  holes  in  a 
model,  there  is  usually  a choice  of  several  ways  in  which 
these  may  be  transferred.  The  choice  of  method  is  influ- 
enced greatly  by  the  shape  of  the  work  and  the  character  of 
the  holes  in  it.  When  the  holes  pass  clear  through  the 
work,  work  and  jig  may  often  be  clamped  together  and  the 
holes  transferred  by  drilling  and  reaming.  Start  the  hole 
with  a drill  that  fits  the  hole  in  the  work;  when  the  jig  has 
been  spotted  sufficiently  deep,  use  a drill  one  size  smaller 
and  finish  with  a rose  reamer  that  closely  fits  the  hole  in 
the  work.  All  holes  having  been  drilled  and  reamed,  en- 
large the  holes  in  the  jig  by  counterboring  with  a counter- 
bore whose  teat  closely  fits  the  reamed  hole. 

64.  When  the  hole  in  the  work  is  blind,  i.  e.,  when  it 
does  not  pass  clear  through,  as  the  hole  a in  Fig.  25,  or 
when  other  circumstances  prevent  a drill  and  reamer  from 
passing  through  the  hole  from  below,  as  in  case  of  the 


32 


JIGS  AND  JIG  MAKING. 


§31 


hole  b,  a different  way  of  transferring  must  be  adopted. 
The  most  common  way  is  to  transfer  the  holes  as  accurately 
as  circumstances  permit  to  the  outside  of  the  jig  by  scribed 
lines.  A so-called  pilot  hole,  as  a'  or  b\  somewhat  larger 
than  the  hole  in  the  work,  is  next  drilled  through  the  jig. 


up 

ar 

ft' 

Fig.  25. 

The  jig  is  then  strapped  to  the  face  plate  and  trued  up  by 
the  holes  in  the  work,  or,  if  an  indicator  cannot  be  applied 
to  the  holes,  a cylindrical  plug  is  inserted  and  the  indicator 
applied  to  the  plug.  After  the  jig  is  trued,  the  plug  is 
removed;  the  hole  in  the  jig  is  then  brought  in  line  with 
that  in  the  model  by  careful  boring. 

65.  When  the  jig  is  too  large  to  be  swung  in  the  lathe, 
or  when  no  lathe  is  available,  the  holes  in  the  jig  may  be 
brought  in  line  by  counterboring.  In  some  cases,  the  holes 


Fig.  26. 


in  the  model  are  deep  enough  to  allow  an  ordinary  counter- 
bore to  be  used;  to  insure  good  work,  the  teat  of  the  coun- 
terbore must  be  a good  fit  in  the  holes  in  the  model.  Owing 
to  the  fact  that  the  holes  are  not  in  line,  the  counterbore 
does  not  cut  equally  all  around  and  will  have  a tendency 


JIGS  AND  JIG  MAKING. 


33 


§ 31 


to  spring  toward  the  side  where  the  least  metal  is  to  be 
removed.  This  tendency  can  be  counteracted  to  a great 
extent  by  forming  the  cutting  edges  in  the  manner  shown 
in  Fig.  26.  That  is,  instead  of  making  them  at  a right 
angle  to  the  axis,  they  are  to  be  inclined  inwardly  toward 
the  shank.  With  a counterbore  made  as  shown,  and  with  a 
reasonable  degree  of  care  while  using  it,  a very  good  job 
can  be  done. 


66.  When  the  holes  in  the  model  are  not  deep  enough 
to  allow  an  ordinary  counterbore  to  be  used,  a special  counter- 
bore made  as  shown  in 
Fig.  27  can  often  be 
employed.  In  this 
case,  the  teat  is  sta- 
tionary; it  is  formed 
by  a well-fitting  plug 
inserted  in  the  hole  in  the  model.  The  counterbore  is  bored 
out  to  fit  this  plug  and  revolves  around  it  in  use.  Its  cut- 
ting edges  should  be  formed  in  the  same  manner  as  those  of 
the  counterbore  shown  in  Fig.  26,  and  for  the  same  reason. 


Fig.  2? 


MARKING  AND  RECORDING  JIGS. 

67.  Marking  Jigs. — An  important  element  in  making 
jigs  and  fixtures  is  the  marking  by  which  they  may  be  iden- 
tified. All  jigs  and  fixtures  should  have  the  name  of  the 
machine  and  the  part  of  the  machine  for  which  they  are 
intended  stamped  on  them,  so  that  any  person  can  tell  just 
what  piece  of  work  the  jig  is  intended  for.  It  is  also  well 
to  stamp  the  size  of  all  drills  and  reamers  opposite  the  bush- 
ings through  which  they  are  to  be  used. 

68.  Recording  Jigs. — It  is  well  to  give  all  jigs  con- 
secutive numbers  and  to  keep  a record  of  them  in  proper 
books  or  card  indexes.  In  some  cases  information  concern- 
ing the  jig  is  entered  on  the  drawing.  Each  jig  should  have 
its  place  in  the  tool  room  or  storage  room,  and  this  should 
be  entered  in  the  record. 


INDEX 


NOTE. — All  items  in  this  index  refer  first  to  the  section  (see  the  Preface)  and  then 
to  the  page  of  the  section.  Thus,  “Belting,  24  45”  means  that  belting  will  be 
found  on  page  45  of  section  24.  As  there  are  two  papers  in  this  volume  bearing  the  sec- 
tion number  18,  all  items  referring  to  the  paper  on  Grinding  have  the  letter  “ G ” 
following  the  section  number  in  this  index. 


A 

Sec.  Page 

Sec. 

Page 

Abrasive  materials 

18  G 

7 

Babbitt  metal,  Lubricants  for 

Abrasives,  Artificial 

18  G 

10 

cutting 

24 

43 

Accumulation  of  errors 

25 

10 

“ metal,  Making  of 

24 

61 

“ of  errors,  Re- 

“  metal,  Melting  of  ..  .. 

24 

62 

duction  of 

25 

12 

Babbitting,  Form  of  box  for.. . 

24 

63 

Addendum  

17 

6 

“ jigs 

24 

65 

“ circle  

17 

6 

“ journal  brasses 

24 

68 

Adjustable  dies 

26 

6 

“ Mandrels  for 

24 

64 

“ reamers 

26 

11 

Back  of  a file 

20 

28 

“ reamers 

26 

28 

“ rest  for  grinding 

19 

28 

“ taps 

25 

30 

Backing  off  attachment  for 

Alligator  wrench 

21 

34 

lathe  

27 

11 

Allowance  for  different  classes 

“ off  cutters,  Methods 

of  fits 

22 

35 

of 

19 

59"" 

Angle  of  clearance  for  hob- 

“  off  machine 

27 

11 

forming  tool 

27 

21 

Backlash  

17 

6 

“ Originating  a 60° 

28 

30 

Ball  bearings,  Grease  for 

24 

36 

Angles,  Laying  out  of 

28 

20 

“ peen  hammer 

20 

2 

“ Originating 

28 

26 

Bars,  Pinch 

24 

2 

Angular  gauges,  Names  of 

28 

20 

Bearings,  Curing  of  hot 

24 

38 

Animal  oils.  Objections  to 

24 

36 

“ Distance  between,  on 

Appliances  for  erecting  an 

shafting 

24 

50 

engine  on  foundation 

23 

39 

“ Grease  for  ball  

24 

36 

Arc  of  contact  of  belt 

24 

46 

“ Oil  for  cleaning 

24 

37 

Artificial  abrasives 

18G 

10 

Bed,  Leveling  a planer 

23 

14 

Automatic  cross-feed  for 

“ of  a punching  machine 

29 

3 

grinding  machine 

18(7 

52 

Bell  chuck  for  grinding 

19 

44 

“ dies 

30 

9 

Bellied  file 

20 

28 

“ gear-cutter 

18 

13 

Belt,  Arc  of  contact  of 

24 

46 

“ Effective  pull  of  a 

24 

46 

B 

Sec. 

Page 

“ Length  of , 

24 

45 

Babbitt  metal 

24 

61 

“ speed 

24 

48 

“ metal,  Composition  of 

24 

61 

Belting 

24 

45 

xiii 


XIV 


INDEX 


Sec. 

Pa/re 

Sec. 

Page 

Belts,  Double 

24 

49 

Boiler  locomotive.  Placing  of. . 

23 

56 

44  Horsepower  of 

24 

48 

44  Placing  of,  in  locomo- 

“  Polishing 

186 

20 

tive  erection 

23 

46 

“ Width  of. 

24 

48 

44  Testing  of  locomotive  . . 

23 

52 

Bench  centers 

20 

5 

Bolster  of  a punch 

29 

3 

“ Post  work 

20 

16 

Bonds  for  emery  wheels 

186 

11 

“ work 

20 

1 

Bort 

19 

68 

“ work,  Tools  used  in 

20 

2 

Bowline  knot 

24 

13 

Benches  for  holding  work 

20 

12 

Box  jigs 

31 

2 

“ Permanent  work 

20 

13 

44  Re  babbitting  a 

24 

68 

“ Portable  work 

20 

14 

Boxes,  Tote 

24 

56 

Bending 

30 

2 

Brass,  Square-thread  taps  for 

25 

38 

“ dies  

30 

6 

Brasses,  Babbitting  journal... . 

24 

68 

Bends 

24 

11 

Brazing  broken  castings 

24 

33 

24 

38 

Breast  drill 

21 

9 

Bevel  gear-blanks,  Laying  out 

Brick  floors  for  erecting 

22 

17 

of 

17 

38 

British  classification  of  files.. 

20 

32 

“ gear-calculations 

17 

35 

Broach,  Simple  square 

21 

9 

“ gear-cutter,  Bilgram 

18 

30 

44  teeth,  Angle  of 

21 

14 

“ gear-teeth,  Convergence 

Broaches,  Grinding  the  teeth 

of 

17 

35 

of 

21 

11 

“ gears 

17 

33 

44  Lubrication  of 

21 

14 

“ gears,  Conjugate 

18 

38 

44  Making  a set  of 

21 

11 

“ gears,  Cutting,  with 

44  Use  of  several,  in  a 

formed  cutters 

18 

14 

set 

21 

10 

“ gears,  Herring-bone 

18 

38 

Broaching 

21 

9 

41  gears,  Laving  out. 

17 

35 

<1 

30 

31 

“ gears,  Laying  out  tooth 

44  kevways 

21 

12 

curves  for 

17 

39 

44  Machine 

21 

13 

“ gears,  Molding  milling. . 

18 

36 

Brown  & Sharpe  gear-cutters 

18 

6 

“ gears,  Pitch  circle  for. ... 

17 

34 

Browning  iron  and  steel 

24 

71 

44  gears,  Pitch  cones  for 

17 

34 

Brush  wheels 

186 

24 

“ gears,  Selecting  cutter 

Buffing 

186 

22 

for 

18 

14 

44  Applications  of 

186 

23 

“ gears,  Setting  milling 

44  Distinction  between 

machine  to  cut 

18 

15 

polishing  and 

186 

22 

“ gears,  Spiral 

18 

38 

44  Material  used  for 

186 

23 

Bilgram  bevel  gear-cutter 

, 18 

30 

44  wheel  mount 

186 

24 

Black  diamond 

19 

68 

44  wheels 

186 

22 

44  lead  

24 

38 

Bulldozer  dies,  Special 

30 

8 

Blackening  iron  and  steel 

24 

71 

Bushing  emery  wheels 

186 

13 

Blackwall  hitch 

24 

11 

44  Facing  of,  by  grinding 

19 

18 

Blank  holder 

30 

14 

Bushings,  Clamp 

31 

10 

Blanks  for  drawing  and  form- 

14 Grinding  of 

31 

12 

ing,  Size  of 

30 

26 

44  Guide  for  jigs 

31 

6 

Block  and  tackle 

22 

39 

44  Material  for 

31 

12 

44  Filing 

20 

28 

44  Permanent  guide  .. . 

31 

6 

Blocking 

22 

1 

44  Removable  jig 

31 

8 

“ Cylindrical  iron 

22 

4 

44  Size  of  guide  hole  in 

31 

11 

44  Iron 

22 

3 

Button  method  of  locating  holes 

“ Wooden 

22 

2 

in  a jig 

31 

28 

Blocks,  Adjustable  parallel 

22 

5 

44  Chain 

22 

39 

44  Parallel 

22 

3 

C 

Sec. 

Page 

Bluing  iron  and  steel 

24 

70 

Caliper  gauge,  Grinding  a 

19 

22 

Blunt  file 

20 

28 

44  Gear-tooth 

18 

17 

INDEX 


XV 


See. 


Cam  for  making  formed  cut- 
ters  27 

Cant  file 20 

Cape  chisel 20 

Capscrew  heads 24 

Carborundum 18^P 

Card,  File 20 

Carriage,  Squaring  lathe,  with 

spindle....’ 23 

Castings,  Brazing  of 24 

“ Cleaning  of 24 

“ Pickling  solutions  for  24 

“ Precautions  in  re- 
gard to  planer 23 

Catspaw 24 

Celluloid  wheels 18(7 

Center,  Cup 20 

“ indicator 25 

“ punch .....  20 

Centers,  Bench 20 

“ Driving  work  be- 

tween, on  grinding 

machine 19 

“ Grinding  of 19 

Chain  block.  Differential 22 

“ blocks  22 

“ hoists 24 

“ tongs 21 

Chaser  hobs 25 

Chatter  marks  from  grinding  19 

Chattering  of  reamers 26 

Cheapening  work  by  duplica- 
tion  24 

Chipped  castings,  Patching  of  24 

Chipping 20 

“ Examples  of 20 

“ Holding  hammer  and 

chisel  in 20 

“ keyseats 20 

“ large  flat  surfaces 20 

“ Pneumatic  hammer 

for 20 

“ strip 20 

Chisel,  Cape 20 

“ Diamond-pointed 20 

“ Flat 20 

“ Gouge 20 

“ Grooving 20 

“ Holding,  while  chip- 
ping   20 

“ Side 20 

Chisels,  Cold 20 

Chuck,  Bell,  for  grinding 19 

“ Grinding  work  held 

in  a 19 

Chucks  for  use  in  grinding 19 


Sec.  Page 


Chucks,  Special,  for  grinding. . 19  25 

Chucking  reamers 26  27 

Circle,  Addendum 17  6 

“ Dividing,  by  assembly 

of  equal  pieces 27  30 

“ Dividing,  by  contact 

measurements 27  26 

“ Dividing,  by  cord  meas- 
urements  27  28 

“ Dividing,  by  correcting 

the  accumulated  er- 
rors   27  32 

“ Dividing,  by  mechani- 

cal correction  of 

errors 27  24 

“ Pitch 17  4 

“ Root 17  6 

Circles,  Dividing  of 27  23 

“ Locating  the  centers  of  21  42 

“ Subdividing  of 21  43 

Circular  pitch 17  5 

“ pitch,  Proportions  of 

gear-teeth  for 17  8 

“ rack 18  28 

Clamp  bushings 31  10 

“ jigs 31  2 

Clamping  devices  for  bench 

work 20  8 

devices  for  jigs. . . . 31  12 

Cleaning,  Compressed  air  for. . 24  21 

“ work  and  castings.  . 24  18 

Clearance 17  7 

“ Angle  of,  for  hob- 
forming tool 27  21 

“ Giving  of,  to  dies.. . . 29  30 

“ of  milling  cutters. . . 27  3 

“ of  reamers 26  15 

“ Providing  of,  in 

grinding  cutters..  19  62 

Clough  duplex  gear-cutter 18  10 

Coal  oil 24  37 

Coining  dies 29  7 

“ dies 30  33 

“ process 30  31 

Cold  chisels 20  16 

Collapsing  taps 25  33 

Coloring 18(7  23 

Combination  dies 29  7 

“ jigs 31  1 

Compound  dies 29  7 

“ dies 29  18 

Compressed  air  for  cleaning. . . 24  21 

Concrete  floors  for  erecting 22  17 

Cones,  Rolling 17  33 

Conical  grinding 18(7  42 

“ work,  Grinding  of 19  21 


Page 

16 

33 

18 

10 

47 

33 

18 

19 

12 

11 

13 

4 

18 

2 

5 

16 

24 

4a 

39- 

5 

34 

29 

9 

12 

29 

32 

19 

21 

19 

22 

22 

24 

24 

18 

18 

16 

18 

18 

19 

18 

16 

44 

24 

44 


XVI 


INDEX 


Sec. 

Page 

Sec. 

Page 

Conjugate  bevel  gears 

18 

38 

Cutters  for  bevel  gears,  Se- 

“  tooth  method  of 

lecting  

18 

14 

gear-cutting 

18 

3 

“ Gang,  for  gears 

18 

9 

“ tooth  method  of 

“ Grinding  cylindrical 

19 

50 

gear-cutting 

18 

22 

“ Grinding  of  clearance 

25 

3 

on  

19 

62 

Corundum 

18  G 

7 

“ Grinding  of  in  place.. 

19 

63 

“ Grading  of 

18£? 

9 

“ Formed 

27 

10 

“ Properties  of 

18G 

8 

“ formed,  Sharpening 

Cost  of  construction 

24 

28 

of 

19 

61 

“ of  pattern  work 

24 

29 

“ Lapping  holes  of  mill- 

Counterbore, Solid 

26 

35 

ing  

19 

66 

“ Two-lipped  flat. . 

26 

35 

“ Laying  out  of  formed 

Counter  bores 

26 

35 

milling 

27 

14 

“ Built-up 

26 

37 

“ Methods  of  backing 

“ Inserted  cutter 

26 

38 

off 

19 

59 

“ Inserted  teeth.. 

26 

37 

“ milling,  Backing  off 

Cow  bar 

24 

3 

of  formed 

27 

11 

Crane 

24 

13 

“ milling,  Grinding,  in 

“ Electric  traveling 

22 

45 

universal  grinding 

“ Hand  traveling 

22 

43 

machine 

19 

57 

“ Jib 

22 

41 

“ milling,  Grinding 

“ Power  traveling 

22 

44 

teeth  of  side 

19 

55 

Cranes  

22 

41 

“ Milling,  with  helical 

Crank  arm,  Laying  out  of  a. . . 

21 

55 

cutting  edges 

27 

6 

“ shaft  of  an  engine,  Fit- 

“  Numbers  of  cutting 

ting  the 

23 

31 

edges  for  milling. . . 

27 

1 

“ shaft,  Squaring  the 

23 

32 

“ Standard  for  gear- 

Cross-filing  

20 

38 

cutting  

18 

5 

Crosshead,  Laying  out  of  a 

21 

56 

“ Tempering  o f mill- 

Cross-peen hammer 

20 

2 

ing  

27 

3 

“ rail  of  planer,  Squaring 

“ with  inserted  teeth. 

of 

23 

16 

Milling  

27 

5 

Crown  gear  

18 

28 

Cutting  a large  spur  gear 

22 

26 

Cupboards,  Tool 

24 

58 

“ bevel  gears,  with 

Cup  center 

20 

4 

formed  cutters 

18 

14 

“ wheel.  Use  of,  in  grind- 

“ dies 

29 

7< 

ing 

19 

55 

“ dies 

29 

11 

Curling 

30 

10 

“ edges  for  mills  with 

“ dies 

29 

7 

inserted  cutters, 

“ dies 

30 

11 

Number  of 

27 

8 

“ dies,  Tapering 

30 

12 

“ edges  for  milling  cut- 

Curves, Filing  of 

20 

43 

ters,  Helical 

27 

4 

Cutter,  Gang  gear,  Gould  and 

“ edges  for  milling  cut- 

Eberhardt  

18 

11 

ters,  Helical 

27 

6 

“ gear,  Clough  duplex... 

18 

10 

“ edges  for  milling  cut- 

“  grinding 

19 

47 

ters,  Number  of 

27 

1 

“ grinding  machine 

19 

48 

“ edges  for  reamers. 

“ grinding,  Position  of 

Helical 

26 

17 

guide  finger  dur- 

“  edges  for  reamers, 

ing 

19 

51 

Number  of 

26 

13 

“ Setting  the  gear,  for 

“ edges,  Number  of,  in 

depth 

18 

8 

dies 

26 

1 

Cutters,  Cams  for  making 

“ edges  of  reamers, 

formed 

27 

16 

Spacing  of 

26 

12 

“ Fly 

27 

9 

“ racks 

18 

18 

INDEX 


XVII 


Sec. 

Page 

Sec. 

Page 

Cutting  speed  for  internal 

Die,  Laying  out  a simple 

29 

23 

grinding 

19 

38 

“ Making  a solid 

26 

2 

“ worm-wheels  with  a 

“ Making  the 

29 

27 

formed  cutter 

18 

36 

“ Meaning  of  the  term 

29 

1 

Cycloid,  Definition  of 

17 

26 

“ Plain  forming 

30 

4 

Cycloidal  odontograph  table, 

“ Position  of  gauge  pin  for 

29 

23 

Grant’s 

17 

27 

“ Simple  forming 

30 

2 

“ system  of  gear-teeth 

17 

18 

“ sinking 

20 

25 

“ system  of  gear-teeth 

17 

26 

“ spring,  Proportions  of.  ... 

26 

7 

“ teeth,  Laying  out  . . 

17 

26 

“ stock  and  round  dies 

21 

29 

Cylinder,  Lining  an  engine, 

“ stock  and  square  dies 

21 

28 

with  the  guides  . . 

23 

30 

Dies,  Adjustable 

26 

6 

“ oil  

24 

36 

“ and  die  stock 

21 

28 

Cylinders,  Fitting  on  vertical 

“ and  punches 

29 

1 

engine 

23 

42 

“ Attachments  used  on 

29 

10 

“ Lagging  of  steam  . . 

24 

54 

“ Automatic 

30 

9 

“ Lining  locomotive.. 

23 

47 

“ Bending 

30 

6 

“ locomotive,  Placing 

“ Classification  of 

29 

6 

of 

23 

55 

“ Coining 

29 

7 

“ Pitch  of 

17 

4 

“ Coining 

30 

33 

“ Placing  of,  in  loco- 

“ Combination....- 

29 

7 

motive  erection.. 

23 

47 

“ Combination  cutting  and 

“ Repairing  leaky. . .. 

24 

33 

drawing 

30 

17 

Cylindrical  grinding 

18G 

42 

“ Comparison  of  fastenings 

“ iron  blocking 

22 

4 

for 

29 

4 

“ Compound 

29 

7 

D Sec. 

Page 

“ Compound 

29 

18 

Decimals,  Reading  of 

25 

6 

“ Curling 

29 

7 

Dedendum  or  root 

17 

6 

“ Cutting 

29 

7 

Definite  gauges 

28 

2 

“ Cutting 

29 

11 

Depth  of  cut  for  gears 

18 

8 

“ Degree  of  accuracy  re- 

Derrick, Description  of 

24 

13 

quired  in 

29 

9 

“ Dismantling  a 

24 

17 

“ Design  of 

29 

8 

“ Erection  of  a 

24 

13 

“ Discharge  of  work  from 

30 

26 

“ mast  

24 

13 

“ Drawing 

29 

7 

Design  of  milling  cutters  with 

“ Economy  of  use  of  stock 

inserted  teeth 

27 

5 

in 

29 

21 

“ of  tools 

25 

2 

“ Embossing 

30 

9 

Diagonal  filing 

20 

41 

“ Essential  parts  of  plain  . . 

29 

11 

Diameter,  Pitch 

17 

5 

“ Fastening  for 

29 

4 

“ Pitch,  of  a worm 

17 

46 

“ for  can  tops,  Forming .... 

30 

4 

Diameters  of  gears  for  fixed 

“ for  curling 

30 

11 

center  distances 

17 

17 

“ for  drop  forging 

30 

34 

Diametral  pitch 

17 

5 

“ for  forming 

30 

2 

Diamond,  Black 

19 

68 

“ for  thread  cutting 

26 

1 

“ pointed  chisel 

20 

18 

“ for  tube  squirting 

30 

35 

“ tools,  Lapping  of  — 

19 

68 

“ Forming 

29 

7 

Die,  Adjustable  pipe 

21 

32 

“ Forming,  Difference  in 

“ Combination  cutting, 

shape  of  upper  and 

drawing,  and  embossing 

30 

22 

lower  portions  of 

30 

7 

“ Dip  or  shear  of 

29 

13 

“ Forms  of 

29 

5 

“ Gauge 

29 

13 

“ Gang 

29 

8 

“ Gauge  pin  for 

29 

11 

“ Gang 

29 

15 

“ Guide  strip  for 

29 

11 

“ Giving  clearance  to 

29 

30 

“ holders 

26 

9 

4‘  Hardening  and  temper- 

41 Inserted-blade  adjustable 

26 

8 

ing  of  ..., 

29 

30 

XV111 


INDEX 


Sec. 


Dies,  Inserted-blade 26 

“ Laying  out  compound 29 

“ Laying  out  of  29 

“ Laying  out  progressive..  29 

“ Method  of  fastening 29 

“ Non-adju  stable 26 

“ Number  of  cutting  edges 

of 26 

“ Operation  of  cutting 

drawing 30 

“ Plain  29 

“ Progressive 29 

“ Progressive 29 

“ Rake  of  cutting  edges  of  26 

“ Redrawing 30 

“ Seaming 30 

“ Self-centering 29 

“ Shear  or  dip  of 29 

“ Special  bulldozer 30 

“ Spring 26 

“ Spring  drawing 30 

“ Spring  drawing 30 

“ Tapering  curling 30 

“ Temper  required  in 29 

“ Triple-action  drawing  .. . 30 

Differential  chain  block 22 

“ chain  hoist 24 

Dimensioning  drawings 25 

Dip  of  a die 29 

“ of  dies 29 

Disk  grinders 186 

“ grinding 18  6 

Dividing  circles 27 

Division  of  lines 27 

“ of  lines,  Mechanical. . 27 

Double-action  press 30 

“ belts 24 

“ cut  files 20 

“ hitch . 24 

Dowel-pins,  Use  of,  in  engine 

erection 23 

Draw-filing 20 

“ filing 20 

Drawing 30 

“ dies 29 

“ dies 30 

“ dies,  Triple-action — 30 

“ Object  of 30 

“ process 30 

“ Size  of  blanks  for 30 

“ work  with  tapered  or 

curved  walls 30 

Drawings,  Dimensioning  of  . . . 25 

Drifting 21 

Drill,  Breast 21 

“ Crank-driven  portable. . 21 


Sec.  Page 


Drill  jigs 

31 

1 

“ Multiple-lip  twist 

26 

27 

“ Scotch 

21 

8 

* Drilling  crow '. 

21 

8 

“ ratchets 

21 

6 

“ ratchets,  Use  of 

21 

6 

Driving  fits 

22 

29 

“ fits,  Allowance  for 

22 

35 

Drop  forgings 

30 

34 

Drying  ovens  used  in  galva- 
nizing  

24 

22 

Duplication  system  of  gear- 
cutting  

18 

1 

E 

Sec. 

Page 

Earth  floors  for  erecting 

22 

15 

Electric  traveling  crane 

22 

45 

Embossing 

30 

2 

“ dies 

30 

9 

Emery 

18  6 

9 

“ Grade  of,  for  lapping. . . 

19 

64 

“ wheel,  Parts  of 

186 

11 

“ wheel,  Sizing  power  of 

19 

27 

“ wheels,  Bonds  for 

186 

11 

“ wheels,  Bushing  of 

186 

13 

“ wheels,  Classification 

of 

186 

11 

“ wheels,  Grading 

186 

15 

“ wheels,  Hand  surfacing 

machines  using 

186 

28 

“ wheels.  Manufacture  of 

186 

11 

“ wheels,  Preparation  of 

186 

13 

“ wheels,  Testing  of , 

186 

17 

“ wheels,  Truing  of 

186 

14 

Engine,  Appliances  for  erect- 
ing, on  foundation. . 

23 

39 

“ Babbitting  boxes  of . . 

24 

66 

“ bed,  Fitting  of,  t o 

cylinder 

23 

28 

“ bed,  Laying  out  of  an 

21 

59 

1,1  bed,  Lining  of,  with 

cylinder 

23 

29 

“ bed,  Preparation  of, 

for  erection 

23 

27 

“ bed,  Work  necessary 

on  vertical 

23 

42 

“ Dismantling  a vertical 

23 

44 

“ Dismantling  of 

23 

37 

“ Erecting  a vertical,  on 

foundation 

23 

46 

“ Erecting  a vertical 

stationary 

23 

41 

“ erection 

23 

26 

“ erection,  Equipment 

for 

23 

26 

Page 

4 

27 

21 

24 

3 

2 

1 

18 

11 

8 

15 

2 

28 

10 

17 

32 

8 

6 

15 

18 

12 

8 

25 

40 

5 

4 

13 

32 

30 

42 

23 

34 

34 

19 

49 

30 

11 

34 

40 

44 

13 

7 

15 

25 

14 

13 

26 

21 

4 

9 

9 

8 


INDEX 


XIX 


Sec.  Page 

Sec. 

Page 

Engine, 

Erection  of  a horizon- 

Erection  of  lathes,  Systems  of 

23 

1 

tal  stationary 

23 

27 

“ of  planers  having 

Erection  of,  on  foun- 

legs 

23 

19 

dation 

23 

38 

“ Systems  of  planer. . . 

23 

10 

“ 

Fitting  guides  and 

Errors,  Accumulation  of 

25 

10 

cylinders  of  vertical 

23 

42 

“ Reduction  of  accumu- 

Fitting the  crank- 

lating  

25 

12 

23 

31 

Expanding  reamer 

26 

29 

“ 

Fitting  the  flywheel 

External  grinding 

18  G 

42 

of 

23 

34 

“ grinding 

19 

16 

“ 

Fitting  the  reciproca- 

“ lapping 

19 

65 

ting  parts  of 

23 

33 

Eye  splice 

24 

6 

Foundation  bolt  am- 

plet  for 

23 

37 

F 

Sec. 

Page 

** 

Gear-cutting 

18 

12 

Face  of  tooth 

17 

7 

lagging,  Placing  of... 

23 

35 

“ plate,  Grinding  work  on  a 

19 

24 

Oiling  devices  for 

23 

34 

“ plate  work  in  grinding. . . 

19 

45 

44 

Oiling  devices  for  ver- 

Feed,  Automatic  cross,  for 

tical 

23 

44 

grinding  machine 

186 

52 

“ 

Painting  and  finishing 

Feeds  used  in  grinding 

19 

8 

of  

23 

37 

Fellows’  gear-shaper 

18 

23 

“ 

Placing  on  dead  cen- 

File,  Advantage  of  convex  face 

ter 

23 

35 

of 

20 

35 

Placing  reciprocating 

“ Back  of 

20 

28 

parts  on  vertical 

23 

43 

“ Bastard 

20 

30 

Squaring  the  crank- 

“  Bellied 

20 

28 

shaft  of 

23 

32 

“ Blunt 

20 

28 

Use  of  dowel-pins  in 

23 

34 

“ Cant 

20 

33 

“ 

valves.  Setting  of 

23 

36 

“ card 

20 

47 

Epicycloid 

17 

26 

“ Coarse 

20 

30 

Equaling  file 

20 

28 

“ Coarseness  of  cut  of 

20 

30 

“ 

file 

20 

33 

“ Dead  smooth 

20 

30 

Erecting 

a gin  pole 

24 

14 

“ Equaling 

20 

28 

a large  rope  wheel... 

22 

27 

“ Equaling 

20 

33 

Earth  floors  for 

22 

15 

“ Flat 

20 

33 

“ 

floor,  Double-plank... 

22 

15 

“ Float 

20 

28 

floor,  Single-plank 

22 

15 

“ Half-round 

20 

33 

*• 

floor,  Wooden-block 

22 

17 

“ Hand 

20 

33 

floors 

22 

14 

“ handle.  Special 

20 

36 

floors,  Brick 

22 

17 

“ handles,  Wooden 

20 

35 

floors,  Cast-iron  plate 

22 

18 

“ Holding  the 

20 

37 

floors,  Concrete 

22 

17 

“ Hopped , 

20 

28 

“ 

jacks,  Heavy 

22 

10 

“ Middle  cut 

20 

29 

“ 

jacks,  Simple 

22 

9 

“ Mill 

20 

33 

“ 

large  flywheel 

22 

25 

“ Pillar 

20 

33 

pit,  Use  of 

22 

25 

“ Pressure  on 

20 

42 

“ 

pits  

22 

19 

“ Rat-tail 

20 

33 

“ 

trucks 

23 

24 

“ Recut 

20 

29 

Erection,  Comparison  of  two 

“ Rough 

20 

30 

methods  of  loco- 

“  Round 

20 

33 

motive 

23 

56 

“ Round-edged  mill 

20 

33 

Engine 

23 

26 

“ Safe-edged.... 

20 

29 

Locomotive 

23 

46 

“ Second  cut 

20 

30 

«» 

Milling-machine  . . . 

23 

20 

“ Singlecut 

20 

30 

U 

of  a derrick 

24 

13 

“ Size  of  

20 

32 

of  lathes  

23 

4 

“ Smooth 

20 

30 

XX 


INDEX 


Sec. 


File,  Square-blunt 20 

“ Style  of 20 

“ Superfine  (or  super)  cut . . 20 

“ Taper 20 

“ Three-square 20 

“ Triangular 20 

“ Use  of  safe-edge 20 

“ Using  the 20 

Filed  work,  Finishing  of 20 

Files  and  filing 20 

“ British  classification  of ..  20 

“ Care  of 20 

“ Double-cut 20 

“ Float 20 

“ Hand-cut 20 

“ Machine-cut 20 

“ Over-cut 20 

“ Pinning  of 20 

“ Selection  of 20 

“ Use  of 20 

Filing  block 20 

“ broad  surfaces 20 

“ Cross 20 

“ curves  20 

“ Diagonal 20 

“ Definitions  and  terms 

used  in 20 

“ Draw 20 

“ Draw 20 

“ Effect  of  oil  during 20 

“ Fitting  keys  by 20 

“ Height  of  work  during  20 

“ into  corners 20 

“ jigs 20 

41  jigs 31 

“ operations 20 

“ Position  of  body  during  20 

“ Purpose  of 20 

“ slots  with  curved  ends. . 20 

“ stand 20 

“ templet  for  symmetrical 

work 29 

Fillet  of  a gear-tooth 17 

Filling  and  painting  machine 

tools 24 

Filter,  Oil 24 

Finishing  filed  work 20 

Fits,  Allowance  for  different 

classes  of 22' 

“ Driving 22 

“ force,  Allowance  for 22 

“ Press 22 

“ Press . 22 

“ Shrink 22 

“ Shrink 22 

“ shrink,  Allowance  for....  22 


Sec.  Page 


Fits,  Taper-press 

22 

34 

Flanges,  Laying  out  bolt  holes 

in 

21 

53 

Flank ! 

17 

7 

Flat  chisel 

20 

16 

“ file 

20 

33 

“ scraper 

21 

2 

“ surfaces,  Chipping  large. . 

20 

22 

Float  file  

20 

28 

“ files. . 

20 

30 

Floor,  Double-plank  erecting.. 

22 

15 

“ pits 

22 

19 

“ ’ Single-plank  erecting.. . 

22 

15 

“ Wooden-block  erecting 

22 

17 

“ work  

20 

1 

Floors,  brick,  Erecting 

22 

17 

“ cast-iron  plate,  Erecting 

22 

18 

“ Concrete,  for  erecting.. 

22 

17 

“ Erecting 

22 

14 

“ for  erecting,  Earth 

22 

15 

Flutes  for  taps,  Forms  of 

25 

21 

“ for  taps,  Number  of 

25 

21 

Fluting  of  reamers 

26 

14 

Fly  cutters 

27 

9 

Flywheel,  Assembling  of  large 

22 

25 

Fitting  the 

23 

34 

Follow  rest  for  grinding 

19 

28 

Force  fit,  Allowance  for 

22 

35 

Forgings,  Drop 

30 

34 

Formed  cutter  process  of  gear- 

cutting   

18 

2 

“ cutter  process  of  gear- 

cutting  

18 

5 

“ cutters 

27 

10 

“ cutters,  Backing  off 

of 

27 

11 

“ cutters,  Cams  for  ma- 

king  

27 

16 

“ cutters,  milling,  Lay- 

ing out  of 

27 

14 

“ cutters,  Sharpening  of 

19 

61 

“ reamers 

26 

11 

“ reamers 

26 

33 

Forming  dies 

29 

7 

“ dies. . . 

30 

2 

“ dies,  Difference  i n 

shape  of  upper  and 

lower  portions  of.. 

30 

7 

“ dies  for  can  tops 

30 

4 

“ Meaning  of  the  term 

30 

1 

“ Size  of  blanks  for 

30 

26 

“ tool 

27 

17 

Foundation,  Appliances  for 

erectingengine 

on 

23 

39 

44  bolt  templet 

22 

14 

Page 

33 

32 

29 

29 

33 

33 

43 

40 

44 

26 

32 

46 

30 

30 

26 

26 

30 

46 

46 

26 

28 

41 

38 

43 

41 

27 

40 

44 

45 

48 

45 

43 

47 

1 

34 

45 

34 

44 

11 

28 

6 

28 

44 

44 

35 

29 

36 

29 

32 

.29 

36 

37 


INDEX 


xxi 


Sec. 

Page 

Sec.  Page 

Foundation  bolt  templet  for 

Gauges,  Laps  for  ring 

28 

11 

engine 

23 

37 

“ 

Limit  of  variation  for 

“ Erecting  a verti- 

limit 

28 

12 

cal  engine  on  a 

23 

46 

“ 

Making  large  plug. . . . 

28 

8 

“ Erection  of  en- 

“ 

Making  snap 

28 

17 

gine  on  

23 

38 

“ 

Master 

28 

1 

“ Securing  planer 

Materials  used  for 

28 

4 

to 

23 

18 

Names  of  angular 

28 

20 

Foundations,  Machine 

22 

13 

Needless  accuracy  in 

28 

3 

Frames,  locomotive,  Placing  of 

23 

50 

Plug 

28 

6 

“ locomotive,  Placing  of 

23 

55 

Propositions  of  plug 

Friction,  Lubricants  for  redu- 

and  ring 

28 

11 

cing 

24 

35 

Reference 

28 

1 

Ring 

28 

6 

Snap  limit 

28 

16 

G 

Sec. 

Page 

Soft  steel 

28 

5 

Galvanizing 

24 

21 

Special 

28 

42 

“ bath,  Use  of  lead  in 

24 

26 

Taper 

28 

1 

“ Precautions  in 

24 

26 

Taper 

28 

22 

“ Preparation  of 

Working 

28 

2 

iron  for 

24 

21 

Gear 

attachment 

18 

12 

“ Use  of  grease  on 

bevel,  Bilgram  cutter 

bath  during 

24 

24 

for 

18 

30 

Gang  dies 

29 

8 

41 

Bevel,  calculations 

17 

35 

“ dies  

29 

15 

bevel,  Laying  out  blanks 

“ gear-cutter,  Gould  and 

for 

17 

38 

Eberhardt 

18 

11 

blank 

17 

7 

“ gear-cutters 

18 

9 

calculations,  Rules  for.. 

17 

9 

Gashing  worm-wheels 

18 

37 

Crown 

18 

28 

Gauge,  Aging  of 

28 

5 

cutter,  Automatic 

18 

13 

“ dies 

29 

13 

cutter,  Clough  duplex.. 

18 

10 

“ Gear-tooth  depth  . . . 

18 

9 

cutter,  gang,  Gould  and 

“ Grinding  a caliper.  .. . 

19 

22 

Eberhardt 

18 

11 

“ Laying  out  a taper 

28 

24 

cutter,  Setting  the,  for 

“ making 

28 

6 

depth 

18 

8 

“ Making  an  inserted 

cutter,  Swasey 

18 

32 

bushing  ring 

28 

10 

cutters,  Brown  & Sharpe 

18 

6 

“ Making  a plug 

28 

6 

cutters,  Pratt  & Whitney 

18 

6 

“ Making  a solid  ring  . . . 

28 

9 

Cutting  a large  spur 

22 

26 

“ pin  for  die 

29 

11 

cutting,  Conjugate  tooth 

“ pin,  Position  of 

29 

23 

method  of 

18 

3 

“ plate  

29 

13 

cutting,  Conjugate  tooth 

“ Seasoning  of 

28 

5 

method  of 

18 

22 

“ work,  Limits  of  accu- 

cutting, Duplication  sys- 

racy in 

28 

2 

tem  of 

18 

1 

Gauges,  Advantages  of  snap  .. 

28 

15 

U 

cutting  engine 

18 

12 

“ Classes  of  ring 

28 

8 

cutting,  Formed  cutter 

“ Classification  of 

28 

1 

process  of 

18 

2 

“ Definite  and  limit 

28 

2 

cutting,  Formed  cutter 

“ Distinguishing  marks 

process  of 

18 

5 

for  limit 

28 

13 

cutting,  Generation  sys- 

“  for  laying  out  key- 

tem  of 

18 

1 

seats 

21 

60 

U 

cutting,  Generation  sys- 

“  Form  of  snap 

28 

15 

tem  of 

18 

22 

“ Hardened-steel 

28 

4 

it 

cutting,  Hobbing  proc- 

“  Lap  for  finishing  plug 

28 

7 

ess  of 

18 

5 

XXII 


INDEX 


Sec. 

Page 

Sec. 

Page 

Gear 

cutting,  Methods  and 

Gear-tooth  depth  gauge 

18 

9 

processes  of  

18 

2 

“ tooth,  Space  of  

17 

6 

44 

cutting,  Molding  milling 

“ tooth,  Thickness  of 

17 

6 

process  of 

18 

4 

“ wheel,  Definition  of 

17 

3 

14 

cutting,  Molding  milling 

Gearing,  Object  of.. 

17 

1 

process  of 

18 

32 

“ Worm 

17 

41 

44 

cutting,  Molding  planing 

Gears,  Bevel 

17 

33 

process  of  

18 

3 

“ bevel,  Cutting,  with 

44 

cutting,  Molding  planing 

formed  cutters 

18 

14 

process  of  

18 

22 

“ bevel,  Herring-bone 

18 

38 

«4 

cutting,  Single-tooth 

“ bevel,  Laying  out  of 

17 

35 

molding  planing  proc- 

“ bevel,  Molding  milling 

ess  of 

18 

4 

of 

18 

36 

44 

cutting,  Single -tooth 

“ bevel,  Selecting  cutters 

molding  planing  proc- 

for. 

18 

14 

ess  of 

18 

26 

“ bevel,  Setting  milling 

44 

cutting,  Standard  cutters 

machine  to  cut 

18 

15 

for  

18 

5 

“ Conjugate  bevel 

18 

38 

44 

cutting,  Systems  of 

18 

1 

“ Depth  of  cut  for  

18 

8 

44 

cutting,  Templet  grind- 

“ Determining  diameters 

ing  process  of 

18 

21 

of,  for  fixed  center  dis- 

44 

cutting,  Templet  planing 

tances 

17 

15 

process  of 

18 

3 

“ Gang  cutters  for 

18 

9 

44 

cutting,  Templet  planing 

“ internal,  Cutting  of 

18 

24 

process  of 

18 

20 

“ Mesh  of  

17 

3 

44 

Definition  of 

17 

3 

“ Miter  

17 

33 

44 

shaper,  Fellows 

18 

23 

“ Spur 

17 

1 

44 

Spur 

17 

3 

“ Standard  pitches  for  . . . 

18 

7 

44 

teeth,  Calculating  the 

“ Tooth  curves  for,  in 

depth  of 

18 

8 

general  use 

17 

18 

44 

teeth,  Cycloidal 

17 

26 

“ Velocity  ratio  of 

17 

14 

44 

teeth,  Cycloidal  or 

Generation  system  of  gear- 

double-curved system 

cutting 

18 

1 

of 

17 

18 

“ system  o f gear- 

44 

teeth,  Diametral  pitch  of, 

cutting 

18 

22 

Proportions  of 

17 

9 

Gin  pole 

24 

13 

44 

teeth,  Devices  for  draw- 

“ pole,  Erection  of  a 

24 

14 

mg 

17 

18 

Gisholt  tool-grinding  machine 

186 

37 

44 

teeth,  Grant’s  cycloidal 

Glazing,  Cause  of,  in  grinding 

odontograph  table  for 

17 

27 

wheels 

19 

3 

44 

teeth,  Involute  or  single- 

“ of  grinding  wheels  .. . 

186 

26 

curved  system  of 

17 

18 

Gouge 

20 

18 

44 

teeth,  Laying  out  of  ... . 

17 

71 

Gould  and  Eberhardt  gang 

4» 

teeth,  Laying  out  of  in- 

gear-cutter  ... 

18 

11 

volute 

17 

20 

Grade  of  a grinding  wheel 

19 

3 

44 

teeth,  Octoidal 

18 

29 

“ of  wheel  for  tool  grind- 

44 

teeth,  Proportions  of. . . . 

17 

8 

ing  

186 

38 

44 

teeth,  Robinson  odonto- 

Grading emery  wheels 

186 

15 

graph  for 

17 

31 

“ of  grinding  wheels. .. 

186 

25 

44 

teeth,  Single-arcapproxi- 

Graduations  on  grinding  ma- 

mation for 

17 

21 

chines 

19 

14 

44 

teeth,  Walker  odonto- 

Granny’s knot 

24 

13 

graph  chart  for 

17 

32 

Grant’s  cycloidal  odontograph 

44 

teeth,  Wiilisodontograph 

table 

17 

27 

for 

17 

30 

“ involute  odontograph 

44 

tooth  caliper 

18 

17 

table 

17 

22 

INDEX 


XX111 


Sec.  Page 

Sec.  Page 

Grant’s  rule  for  rack  teeth 

17 

25 

Grinding  machine,  Automatic 

Graphite 

24 

38 

cross-feed  for 

186 

52 

Grease 

24 

36 

“ 

machine,  Driving 

“ for  ball  bearings 

24 

36 

work  between  cen- 

“  for  shafting 

24 

37 

ters  on 

19 

16 

“ Use  of,  on  galvanizing 

“ 

machine,  Gisholttool 

186 

37 

bath 

24 

24 

“ 

machine,  Plain 

186 

43 

Greasy  material,  Disposition  of 

24 

40 

“ 

machine,  Seller’s  tool 

186 

35 

Grinders,  Disk 

18  G 

30 

“ 

machine,  Simple 

Grinding,  Absorption  of  vibra- 

hand 

186 

27 

tion,  during 

19 

33 

it 

machine,  Surface. . . . 

19 

46 

“ Advantages  of 

19 

1 

“ 

machine,  Swinging- 

“ Allowance  for,  in 

frame  

186 

29 

reamers 

C6 

17 

“ 

Machine  tool 

186 

34 

“ Applications  of 

186 

19 

“ 

machine,  Universal 

186 

43 

“ Back  rest  for 

19 

28 

“ 

machine,  Universal 

186 

47 

“ caliper  gauges 

19 

22 

“ 

machine,  Universal, 

“ centers 

19 

24 

Using,  as  cutter 

“ Chatter  marks  in  — 

19 

9 

grinder 

19 

57 

“ Chucks  for  use  in. . . 

19 

44 

“ 

machine,  Upright 

“ Classification  ot  rest 

surface 

186 

30 

used  in 

19 

27 

“ 

machine,  Wet,  tool  . 

18G 

33 

“ close  to  a shoulder  . . 

19 

22 

41 

machines,  Adjusting 

“ Comparison  of,  with 

of  

19 

14 

turning 

19 

2 

“ 

machines,  Gradua- 

“  Conical 

186 

42 

tions  on 

19 

14 

“ conical  work 

19 

21 

“ 

material 

186 

1 

“ conical  work 

19 

42 

“ 

Methods  of 

19 

16 

“ Cutter  and  reamer  . . 

19 

47 

“ 

Methods  of 

19 

42 

“ cutters  in  place 

19 

63 

“ 

milling  cutters 

27 

3 

“ cutters,  Position  of 

“ 

Noting  the  sparks 

guide  finger  dur- 

during  

19 

13 

ing 

19 

51 

“ 

Object  of 

186 

19 

“ Cutting  speed  for  in- 

“ 

of  bushings 

31 

12 

ternal  

19 

38 

“ 

of  work  on  face  plate 

19 

45 

“ Cylindrical 

186 

42 

“ 

on  a planer 

19 

45 

“ cylindrical  cutters  . . 

19 

50 

“ 

Poole  method  for, 

“ cylindrical  work 

19 

18 

cylindrical  work . . 

19 

33 

“ Definition  of 

186 

1 

“ 

Possibilities  of 

186 

20 

“ Disk 

186 

42 

II 

Pressure  necessary 

m “ ends  of  work 

19 

18 

for  internal 

19 

37 

“ External 

186 

42 

“ 

Prevention  of  heat- 

“  External 

19 

16 

ing  during 

19 

11 

“ Feeds  used  in 

19 

8 

“ 

Radial 

186 

42 

“ Fixed  rest  for 

19 

28 

“ 

reamers 

19 

54 

fixture,  Internal 

19 

40 

“ 

reamers 

26 

18 

“ Flexible  fixed  rest 

“ 

Rigid  fixed  rest  for. . 

19 

28 

for 

19 

29 

“ 

Selection  of  wheels 

“ Follow  rest  for 

19 

28 

for  external 

19 

5 

“ Hand 

186 

27 

“ 

Selection  of  wheels 

“ Influence  of  tempera- 

for internal 

19 

5 

ture  on 

19 

11 

“ 

Selection  of  wheels 

“ Internal 

186 

42 

for  surface 

19 

47 

“ Internal 

19 

37 

Selection  of  wheels 

‘‘  lathes 

186 

41 

for  tool  

186 

38 

“ machine 

186 

41 

“ 

Set-wheel  method  of 

19 

26 

XXIV 


INDEX 


Sec. 

Page 

Sec. 

Page 

Grind 

ng,  Sizing  power  of 

Grooving  chisel 

20 

18 

wheel  during 

19 

27 

“ reamers 

26 

20 

“ 

solids  of  revolution.. 

18(7 

42 

Guide  bushings  for  jigs 

31 

6 

“ 

Special  chucks  for... 

19  ' 

25 

“ finger.  Location  of,  on 

“ 

Special  rests  for 

19 

33 

universal  grinding  ma- 

“ 

Spring  rest  for 

19 

29 

chine 

19 

59 

“ 

Steadying  of  work 

“ finger,  Mounting  of,  on 

during 

19 

27 

universal  grinding 

11 

Surface 

18(7 

42 

machine 

19 

57 

Surface 

19 

45 

“ finger,  Position  of,  i n 

Surface,  Holding 

cutter  grinding 

19 

51 

work  during 

19 

47 

“ strip  for  die 

29 

11 

“ 

teeth  of  broaches 

21 

11 

Guides,  Lining  of,  on  loco- 

“ 

teeth  of  side  milling 

motive 

23 

50 

cutters 

19 

55 

“ 

Tool 

19 

47 

H 

Sec. 

Page 

“ 

tools 

18(7 

32 

Hack  saws,  Hand 

20 

6 

“ 

tools,  Speed  of  grind- 

“ saws,  Power 

20 

6 

stone  for 

18(7 

5 

Half-round  file 

20 

33 

Universal  back  rest 

Hammer,  Ball-peen 

20 

2 

for 

19 

30 

“ Cross-peen . 

20 

2 

44 

Use  of  cup  wheel  in 

19 

55 

“ Holding,  while  chip- 

44 

wheel,  Combination 

19 

4 

ping 

20 

19 

wheel,  Grade  of 

19 

3 

“ Pneumatic 

20 

24 

wheel,  Influence  of 

“ Straight-peen 

20 

2 

hardness  of  work 

Hand-cut  files 

20 

26 

on 

19 

4 

“ file 

20 

33 

“ 

wheel,  Influence  of 

“ grinding 

18(7 

27 

vibration  of  work 

“ reamer 

21 

15 

on 

19 

4 

“ taps  

25 

23 

“ 

wheel,  Selection  of.. 

18(7 

25 

Handles,  File 

20 

35 

“ 

wheel,  Selection  of.. 

19 

3 

Handy  tackles 

22 

39 

“ 

wheels 

18(7 

7 

Hardening  dies 

29 

30 

“ 

wheels,  Cause  of 

“ of  taps 

25 

25 

glazing  in 

19 

3 

“ the  punch 

29 

32 

“ 

wheels,  Directions 

Hardness,  Scale  of 

18  G 

8 

for  selection  of ... . 

19 

5 

Heads  of  capscrews 

24 

72 

“ 

wheels.  Glazing  of. . . 

18(7 

26 

“ Setting  of  planer 

23 

19 

“ 

wheels,  Grading  of . . 

18(7 

25 

Headstock  spindle,  Making 

“ 

wheels,  Shapes  of 

19 

6 

taper  holes  in  

23 

7 

41 

wheels,  Speeds  of 

18(7 

18 

Headstocks,  Boring  of  lathe.. . 

23 

3 

“ 

wheels,  Truing  of  . . . 

19 

10 

“ Machining  of 

work  held  in  chuck  .. 

19 

24 

lathe 

23 

3 

“ 

work  on  a face  plate 

19 

24 

Heat  insulation 

24 

54 

Grindstone,  Action  of  water 

“ Lubricants  for  removing 

24 

41 

on  a 

18(7 

2 

Heater  for  making  shrink  fits 

22 

38 

41 

Automatic  truing 

Heating,  Prevention  of,  during 

device  for : 

18  G 

3 

grinding 

19 

11 

41 

‘ mountings 

18(7 

3 

Helical  cutting  edges  for  mill- 

41 

Speed  of 

18G 

5 

ing  cutters . 

27 

4 

Truing  of  by  hand 

18(7 

4 

Herring-bone  bevel  gears 

18 

38 

Grindstones  

18(7 

2 

Hexagon,  Laying  out  of 

21 

45 

41 

Artificial 

18(7 

6 

Hitch,  Black  wall 

24 

11 

11 

Composition  of... 

18(7 

2 

“ Catspaw 

24 

11 

“ 

Origin  of 

18G 

2 

“ Double 

24 

11 

41 

Tool  rests  for. . . , 

18(7 

3 

“ Parbuckle 

24 

13 

INDEX 


XXV 


Sec. 

Page 

Sec. 

Page 

Hitch,  Timber 

24 

12 

Internal  gears,  Cutting  of 

18 

24 

Hitches  

24 

11 

“ grinding 

18  G 

42 

Hob  forming  tool 

27 

21 

“ grinding 

19 

37 

“ Number  of  slots  in 

27 

22 

“ grinding,  Cutting 

Hobbed  worm-wheel 

17 

42 

speed  for 

19 

38 

Hobbing  process  of  gear-cut- 

“ grinding  fixture 

19 

40 

ting 

18 

5 

“ grinding,  Pressure 

“ worm-wheels 

18 

37 

necessary  for 

19 

37 

Hobs 

25 

28 

“ lapping 

19 

64 

“ Chaser 

25 

29 

Involute,  Definition  of . 

17 

18 

“ Design  of 

25 

28 

“ odontograph  table, 

“ for  worm-wheels 

27 

20 

Grant’s 

17 

22 

“ Use  of 

25 

28 

“ system  of  gear-teeth 

17 

18 

Hoist,  Differential  chain 

24 

5 

“ teeth,  Base  circle  for 

17 

19 

“ Pneumatic  

22 

40 

“ teeth,  Laying  out  of 

17 

20 

“ Triplex 

24 

5 

Iron,  Blackening  of 

24 

71 

Hoists..  

22 

38 

“ blocking 

22 

3 

“ Chain 

24 

5 

“ blocking,  Cylindrical 

22 

4 

“ Efficiency  of 

24 

5 

“ Bluing  of 

24 

70 

Holder,  Blank 

30 

14 

“ Browning  of 

24 

71 

Hold-downs 

29 

10 

“ Preparation  of,  for  gal- 

Holes, Locating  of,  in  jigs 

31 

26 

vanizing  

24 

21 

Hollow  mill  for  annular  mill- 

ing 

26 

43 

J 

Sec. 

Page 

“ mills 

26 

39 

Jack,  Laying  out 

22 

9 

“ mills,  Inserted-blade.. 

26 

40 

“ Sectional 

22 

9 

Hook  scraper 

21 

3 

“ screws 

22 

10 

Hopped  file 

20 

28 

Jacks 

22 

7 

Horsepower 

24 

47 

“ Heavy  erecting 

22 

10 

“ and  size  of  shaft- 

“  Hydraulic 

22 

12 

ing 

24 

51 

“ Lifting 

22 

10 

“ of  belts 

24 

48 

“ Simple  erecting 

22 

9 

Hot  bearings,  Curing  of. .... 

24 

38 

“ Simple  leveling 

22 

7 

Housings,  Setting  of  planer — 

23 

14 

“ Stone 

22 

11 

Hydraulic  jacks  

22 

12 

“ Track 

22 

11 

k‘  press,  General  con- 

“  Use  of  screw,  in  locating 

struction  of 

22 

31 

centers  of  work 

21 

42 

“ press,  Portable  .... 

22 

31 

Jaws,  Vise 

20 

10 

Hydrofluoric  acid  for  pickling 

24 

20 

Jib  crane 

22 

41 

Hypocycloid 

17 

26 

Jig,  Babbitting 

24 

68 

“ design 

31 

16 

I 

Sec. 

Page 

“ details 

31 

6 

Indicator,  Center 

25 

18 

“ making 

31 

16 

“ Lathe 

25 

14 

“ stops 

31 

3 

Indicators,  Holder  for 

25 

20 

“ Tapping 

21 

20 

Inserted-blade  adjustable  die 

26 

8 

Jigs,  Babbitting 

24 

65 

“ blade  dies 

26 

4 

“ Box 

31 

2 

“ blade  reamers 

26 

11 

“ Clamp 

31 

2 

Inspecting  ropes,  slings,  and 

“ Clamping  devices  for 

31 

12 

lashings 

24 

4 

“ Classes  of 

31 

1 

Inspection  of  lathes 

23 

4 

“ Combination 

31 

1 

“ of  lathes — 

23 

8 

“ Drill 

31 

1 

“ of  milling  machines 

23 

24 

“ Essential  parts  of 

31 

2 

Inspector’s  report  on  lathe.  . . 

23 

10 

“ Filing 

20 

47 

“ report  on  milling 

“ Filing 

31 

1 

machine 

23 

26 

“ General  requirements  of 

31 

3 

XXVI 


INDEX 


Sec. 


Jigs,  Locating  holes  in 31 

“ Locating  holes  in,  by  the 

button  method 31 

“ Locating  holes  in,  from  a 

model 31 

“ Marking  and  recording  of  31 

“ Reaming 31 

“ Size  of  guide  hole  in 31 

“ Stop-pins  for 31 

“ Tapping 31 

“ Types  of 31 

“ Uses  of 31 

Journal  brasses,  Babbitting ...  24 

K Sec. 

Kerosene 24 

Kettle,  Soda 24 

Key,  Sectional. . 24 

Keys,  Fitting,  by  filing 20 

“ Provision  for  withdraw- 
ing   20 

“ Round 20 

“ Taper 20 

“ Woodruff 20 

Keyseats,  Chipping  of 20 

“ Gauges  for  laying 

out 21 

Keyways,  Broaching 21 

Knife-edge  straightedge 28 

Knot,  Bowline 24 

“ Granny’s 24 

“ Square 24 

Knots 24 

L Sec. 

Lagging,  cutting,  and  fitting 

sheet  iron 24 

“ Placing  of  engine  .. . 23 

steam  cylinders  and 

pipes 24 

Land  of  taps 25 

Lap  for  finishing  plug  gauges  28 

“ Using  a 19 

Laps  for  ring  gauges 28 

Lapping 19 

“ a conical  hole 19 

“ circular  arcs 19 

“ diamond  tools 19 

“ External 19 

“ Grade  of  emery  for. . . 19 

“ holes  of  milling  cutters  19 

“ Internal 19 

“ odd  shapes 19 

“ plane  surfaces 19 

“ Purpose  of 19 


See.  Page 


Lapping,  Tools  used  in 

19 

63 

“ valve  seats 

19 

G6 

Lashings,  Inspection  of 

24 

4 

“ Use  of 

Lathe,  Backing-off  attachment 

24 

4 

for 

27 

11 

“ beds,  Machining  of 

23 

2 

“ beds,  Seasoning  of 

23 

1 

“ beds,  Testing  of 

23 

2 

“ erection,  Systems  of 

“ headstocks,  Machining 

23 

1 

of 

23 

3 

“ indicator 

“ Lining  headstock  and 

25 

14 

tail-stock  spindles  of 
“ Squaring  carriage  with 

2 o 

4 

spindle 

23 

7 

“ tail-stocks,  Machining  of 
Lathes,  Boring  holes  for  head- 

23 

3 

stock  spindle 

“ Boring  holes  for  tail- 

23 

3 

stock  spindle 

23 

3 

“ Erection  of 

23 

4 

“ Grinding 

18G 

41 

“ Inspection  of 

23 

4 

“ Inspection  of 

“ Making  taper  holes  in 

23 

8 

headstock  spindle... 

23 

7 

Laying  out  a crank-arm 

21 

55 

“ out  a crosshead 

21 

56 

“ out  a large  journal  cap 

21 

54 

“ out  an  engine  bed 

21 

59 

“ out  appliances,  Special 

21 

52 

“ out  bevel-gear  blanks 

17 

38 

“ out  bevel  gears 

“ out  bolt  holes  for  pipe 

17 

35 

flanges 

“ out,  Coatings  used  to 

21 

53 

make  lines  in 

21 

38 

“ out  ends  for  small  rods 

21 

61 

“ out  jack 

“ out  keyseats,  Gauges 

22 

9 

for 

21 

60 

“ out  of  dies 

“ out  plate  for  general 

29 

21 

work 

“ out  plate  for  heavy 

21 

49 

work 

21 

47 

“ out  plate  for  light  work 

21 

45 

“ out  plate,  Revolving... 

21 

50 

“ out  tools 

21 

39 

“ out  work 

21 

36 

“ out  work,  Divisions  of 

21 

37 

“ out  work,  Examples  of 

21 

53 

“ out  work,  Methods  of 

21 

38 

Lead,  Black 

24 

38 

Page 

26 

28 

30 

33 

1 

11 

15 

1 

2 

1 

68 

Page 

37 

18 

60 

48 

49 

50 

50 

50 

22 

60 

12 

39 

13 

13 

13 

11 

Page 

54 

35 

54 

22 

7 

64 

11 

63 

65 

68 

68 

65 

64 

66 

64 

66 

67 

63 


INDEX 


XXV11 


Sec.  Page 

Lead,  Use  of,  in  galvanizing 


bath 

24 

26 

Leather  wheels 

180' 

24 

Left-handed  taps 

25 

33 

Length  of  tooth 

17 

7 

Leveling  a planer  bed 

23 

14 

“ jacks,  Simple .... 

22 

7 

Lifting  jacks 

22 

10 

Limit  gauges 

“ gauges.  Distinguishing 

28 

2 

marks  for 

“ gauges,  Limit  of  varia- 

28 

13 

ation  for 

28 

12 

“ gauges.  Snap 

Lines,  Dividing,  by  the  correc- 
tion of  accumulated 

28 

16 

errors 

27 

36 

“ Division  ot 

27 

34 

“ Mechanical  division  of. . 

27 

34 

Lining  an  engine 

23 

29 

Locomotive  boiler,  Placing  of 

23 

56 

“ boiler,  Testing  the 

“ cylinders,  Lining 

23 

52 

of 

“ cylinders,  Placing 

23 

47 

of 

23 

55 

“ erection 

“ erection,  Com- 

parison of  two 

23 

46 

methods  of 

“ erection,  Placing 

23 

56 

cylinders  in 

23 

47 

“ frames,  Placing  of 

23 

50 

“ frames,  Placing  of 

“ Lining  the  guides 

23 

55 

of 

“ Placing  the  valve 

23 

50 

gear  on 

23 

55 

Long  splice 

Lubricant  for  cutting  tools,  A 

24 

6 

cheap 

24 

42 

“ Selecting  a 

24 

35 

“ Turpentine  as  a 

24 

43 

Lubricants 

Conditions  under 
which  no,  are  re- 

24 

35 

required  

“ for  carrying  away 

24 

41 

heat 

“ for  cutting  Babbitt 

24 

41 

metal 

24 

43 

“ for  cutting  steel 

“ . for  cutting  wrought 

24 

41 

iron 

“ for  drilling  raw- 

24 

41 

hide  

24 

43 

Sec.  Page 

Lubricants  for  reducing  fric- 


tion  

“ Preventing  waste 

24 

35 

of 

24 

43 

“ Uses  of 

24 

35 

Lubrication  of  broaches 

21 

14 

“ Pipe  system  for. .. 

24 

42 

M 

Sec. 

Page 

Machine,  Adjusting  of  grinding 

19 

14 

“ Backing-off 

27 

11 

“ broaching 

21 

13 

“ cut  files 

20 

26 

“ Cutter  and  reamer 

grinding 

19 

48 

“ foundations  

22 

13 

“ Gisholt  tool-grinding 

18(7 

37 

“ grinding 

“ grinding.  Automatic 

18(7 

41 

cross-feed  for 

18(7 

52 

“ Plain  grinding 

18  G 

43 

“ Seller’s  tool-grinding 

18(7 

35 

“ Simple  hand-grinding 

18(7 

27 

“ Surface  grinding 

19 

46 

“ S w i n gi  n g- f r am  e 

grinding 

18(7 

29 

“ taps 

25 

26 

“ tool  grinding 

18(7 

34 

“ tools,  Painting  of 

24 

28 

“ Universal  grinding  . . 

18(7 

43 

“ Universal  grinding  . . 

18(7 

47 

“ Wet,  tool  grinding. . . 

18(7 

33 

Machines,  Hand-surfacing 

18(7 

28 

“ Inspection  of  milling 

23 

24 

Machining  lathe  beds 

23 

2 

11  of  lathe  tail-stocks 

23 

3 

Mandrels  for  babbitting 

Marking  material  used  in 

24 

64 

scraping 

21 

5 

Marlinspike 

24 

7 

Mast,  Derrick 

24 

13 

Master  gauges 

Material,  Influence  of  hardness 

28 

1 

of,  on  grinding  wheel 

19 

4 

Materials,  Abrasive 

18  G 

7 

“ used  for  gauges 

28 

4 

Matrix  or  die 

Measurements,  Accuracy 

29 

1 

attainable 
in 

28 

3 

“ Approxi- 

mate  

25 

8 

“ Classifica- 

tion of 

25 

8 

“ Precise 

25 

9 

Mechanical  division  of  lines  . . . 

27 

34 

XXV111 


INDEX 


Sec. 

Page 

Sec.  Page 

Mesh 

as  applied  to  gearing. . . . 

17 

7 

Model  for  locating  holes  in  a 

“ 

of  gears 

17 

3 

jig 

31 

31 

Meta! 

, Babbitt,  Composition  of 

24 

61 

Molding  milling  bevel  gears  .. 

18 

36 

Melting  of  Babbitt 

24 

62 

“ milling  process  of 

Micrometer  caliper,  Accuracy 

gear-cutting 

18 

4 

obtainable  with 

28 

3 

“ milling  process  of 

‘ Special  form  of, 

gear-cutting 

18 

32 

for  dividing 

, 

“ planing  process  of 

lines 

27 

36 

gear-cutting 

18 

3 

Middle  cut  file 

20 

29 

“ planing  process  of 

Mill  file 

20 

33 

gear-cutting 

18 

22 

Milling  bevel  gears,  Molding.. 

18 

36 

“ planing  process  of 

*4 

cutter,  Tempering  of.. 

27 

3 

gear-cutting,  Single- 

cutters  

27 

1 

tooth  

18 

4 

“ 

cutters,  Backing-off  of 

“ planing  process,  Sin- 

formed  

27 

11 

gle-tooth  

18 

26 

“ 

cutters,  Clearance  of.. 

27 

3 

“ process  of  gear-cut- 

“ 

cutters,  Grinding,  in 

ting  

18 

22 

universal  grinding 

machine 

cutters,  Grinding  of. . . 
cutters,  Grinding  teeth 
of  side 

19 

27 

19 

57 

3 

55 

N 

Naphtha 

Nicked  teeth  for  milling  cut- 
ters  

Sec. 

24 

27 

Page 

38 

A 

cutters,  Helical  cutting 

edges  for  

27 

4 

cutters,  Lapping  holes 

O 

Sec. 

Page 

in 

19 

66 

Object  of  gearing 

17 

1 

U 

cutters,  Left-handed . . 

27 

4 

Octoidal  teeth  for  gears 

18 

29 

it 

cutters,  Methods  of 

Odontograph  for  gear-teeth. . . 

17 

18 

backing  off 

19 

59 

“ Robinson 

17 

31 

<4 

cutters,  Nicked  teeth 

“ table.  Grant’s 

for 

27 

4 

cycloidal 

17 

28 

4* 

cutters,  Number  of 

“ table,  Grant’s 

cutting  edges  for 

27 

1 

involute 

17 

22 

Cutters,  Right-handed 

27 

4 

“ tables 

17 

18 

44 

cutters,  Spiral 

27 

4 

“ Willis 

17 

30 

44 

cutters  with  helical 

Oil  channels 

24 

39 

cutting  edges 

27 

6 

“ Coal 

24 

37 

cutters  with  inserted 

“ Cylinder 

24 

36 

teeth 

27 

5 

“ Effect  of,  during  filing 

20 

45 

ii 

Hollow  mill  for  an- 

“  filter 

24 

44 

nular 

26 

43 

“ for  general  shop  use 

24 

36 

it 

machine  erection 

23 

20 

“ holes 

24 

39 

t i 

machine,  Setting,  to 

“ Mineral  sperm 

24 

37 

cut  bevel  gears 

18 

15 

“ Paraffin 

24 

37 

44 

machines,  Inspection 

“ separator 

24 

43 

of 

23 

24 

Oiling  devices  for  vertical  en- 

“ 

process  of  gear-cut- 

gine  

23 

44 

ting,  Molding 

18 

32 

Oils,  Objection  to  animal 

24 

36 

ii 

racks 

18 

19 

“ Thinning  of 

24 

37 

Mills,  Inserted-blade  hollow... 

26 

40 

“ Volatile 

24 

38 

“ 

Solid  hollow 

26 

39 

Oilstones,  Artificial 

186 

7 

with  inserted  cutters, 

11  Composition  of 

186 

6 

Number  of  cutting 

“ Kinds  and  qualities 

edges  of 

27 

8 

of 

186 

6 

Miter  gears 

17 

33 

Old  man,  for  use  with  ratchet 

21 

8 

INDEX 


XXIX 


Sec. 

Originating  angles 28 

“ tapers 28 

Overcut  files 20 

P Sec. 

Painting  and  finishing  engines  23 

“ machine  tools 24 

Paraffin  oil 24 

Parallel  blocks 22 

“ blocks,  Adjustable  .. . 22 

Parbuckle 24 

Patching  chipped  castings 24 

Patternwork,  Cost  of 24 

Petroleum,  Refined 24 

Pickle  bed 24 

Pickling  solutions 24 

Pillar  file 20 

Pinning  of  files 20 

Pinch  bars 24 

Pinion 17 

Pipe  cutter 21 

“ die,  Adjustable 21 

“ flanges,  Laying  out  bolt 

holes  in 21 

“ stock 21 

“ Threads,  Tapping  of  — . 21 

“ Threading  of 21 

“ tongs 21 

“ tongs,  Chain 21 

vise 20 

“ vises  21 

“ wrench,  Use  of  rope  as. . . 21 

“ wrenches 21 

Pipes,  Lagging  of  steam 24 

Pit,  Use  of  erecting 22 

Pitch  circle 17 

“ circle  for  bevel  gears 17 

“ Circular 17 

“ Circular,  Proportions  of 

gear-teeth  for 17 

“ cones  for  bevel  gears. .. . 17 

“ cylinders 17 

“ diameter 17 

“ diameter  of  a worm 17 

“ Diametral 17 

“ point 17 

“ Rule  to  change  circular 

to  diametral 17 

“ Rule  to  change  diametral 

to  circular 17 

Pits,  Floor 22 

Plain  dies 29 

“ grinding  machines 18G1 

Planchet 30 

Plane,  Scraping 28 

“ surfaces,  Lapping  of.. . . 19 


Sec. 

Page 

Planer  bed,  Leveling  a 

23 

14 

“ beds,  Supporting  of 

“ castings,  Precautions 

23 

12 

in  regard  to 

“ Erection  of,  on  founda- 

23 

12 

tion  

23 

18 

“ erection.  Systems  of. . . 

23 

10 

“ Grinding  on  a 

19 

45 

“ heads,  Setting  of 

23 

19 

“ housings,  Setting  of 

“ Preparation  of,  for 

23 

14 

shipment 

“ Securing  of,  to  founda- 

23 

17 

tion  

“ Squaring  of  cross-rail 

23 

18 

of 

23 

16 

“ table,  Placing  of 

23 

15 

Planers,  Classes  of 

“ having  legs,  Erection 

23 

11 

of 

Plate  for  laying  out  general 

23 

19 

work 

“ for  laying  out  heavy 

21 

49 

work 

21 

47 

“ Gauge 

“ Laying  out,  for  light 

29 

13 

work 

21 

45 

“ revolving,  Laying  out.. 

“ surface,  Use  of,  in  scra- 

21 

50 

ping  

21 

5 

Plates,  Surface 

21 

40 

Plug  gauge,  Making  a 

28 

6 

“ gauges 

“ gauges,  Lap  for  finish- 

28 

6 

ing 

28 

7 

“ gauges,  Making  large. .. . 

28 

8 

“ gauges,  Proportions  of... 

28 

11 

Plumbago 

24 

38 

Plunger  of  a double  - action 

press 

30 

19 

“ or  punch 

29 

1 

Pneumatic  hammer 

20 

24 

“ hoist 

22 

40 

Pole,  Gin 

Polishing  and  buffing,  Distinc- 

24 

13 

tion  between 

18  G 

22 

“ Material  used  for 

isys 

23 

“ Object  of 

18  G 

20 

“ wheels  and  belts 

Poole  method  of  grinding 

18G 

20 

cylindrical  work 

19 

33 

Portable  work  benches 

20 

14 

Post  work  bench 

20 

16 

Power,  Transmission 

“ transmitted  by  cold- 

24 

45 

rolled  head-shafts  . . . 

24 

51 

Page 

26 

26 

30 

Page 

37 

28 

37 

3 

5 

13 

32 

29 

37 

20 

19 

33 

46 

2 

8 

30 

32 

53 

31 

21 

31 

33 

34 

9 

32 

35 

33 

54 

25 

4 

34 

5 

8 

34 

4 

5 

46 

5 

9 

10 

19 

11 

43 

33 

41 

67 


XXX 


INDEX 


Sec. 

Page 

Sec. 

Page 

Power  transmitted  by  cold- 

Reamer  grinding 

19 

54 

rolled  line  shafting  . . 

24 

53 

“ grinding  machine 

19 

48 

“ transmitted  by  turned- 

“ Hand 

21 

15 

iron  head-shafts 

24 

50 

“ Step 

21 

15 

“ transmitted  by  turned- 

“ Taper 

21 

16 

iron  line  shafting.... 

24 

52 

Reamers,  Adjustable 

26 

11 

44  traveling  crane 

22 

44 

“ Adjustable 

26 

28 

Pratt  & Whitney  gear-cutters 

18 

6 

41  Allowance  for  grind- 

Press. Double-action 

30 

19 

ing 

26 

17 

22 

29 

44  Chattering  of 

26 

12 

“ fits 

22 

32 

44  Chucking 

26 

27 

“ fits,  Taper 

22 

34 

“ Classification  of 

26 

11 

“ General  construction  of 

44  Clearance  of 

26 

15 

hydraulic 

22 

31 

44  Enlarging  worn  solid 

26 

25 

“ Portable  hydraulic 

22 

31 

44  Fluting  of 

26 

14 

“ Single-action 

30 

19 

44  Formed 

26 

11 

Presses,  Object  of  setting,  on 

44  Formed 

26 

33 

an  angle 

30 

26 

44  Four-square 

26 

33 

Prick  punch 

20 

2 

44  Grinding  of 

26 

18 

Profiling  templet  

29 

28 

44  Grooving  of 

26 

20 

Progressive  dies 

29 

8 

44  Gunsmith 

26 

33 

44  dies..  

29 

15 

44  Helical  cutting  edges 

Punch,  Bolster  of  a 

29 

3 

for • 

26 

17 

“ Definition  of 

29 

1 

44  Inserted-blade 

26 

11 

“ Fitting  of  the 

29 

31 

44  Methods  of  backing 

“ Hardening  and  tem- 

off  

19 

59 

pering  of 

29 

32 

44  Number  of  cutting 

“ Prick * 

20 

2 

edges  for 

26 

13 

“ Self-centering 

29 

12 

“ Rose 

26 

26 

“ Spiral 

29 

12 

44  Shell 

26 

25 

Punching  — 

29 

12 

44  Solid 

26 

11 

44  Stepped 

26 

23 

It 

Sec. 

Page 

44  Straight 

26 

11 

Rack 

17 

8 

44  Taper 

26 

11 

“ Circular 

18 

28 

44  Taper 

26 

23 

“ cutting 

18 

18 

44  Temper  of 

26 

22 

“ Determining  thickness  by 

44  Use  of . 

26 

11 

adjustable  parallel 

22 

6 

Reaming,  Advantage  of  verti- 

“  teeth.  Grant’s  rule  for 

17 

25 

cal 

21 

17 

Racks,  Tool 

24 

59 

44  Example  of  vertical 

21 

18 

Radial  grinding 

18G 

42 

44  holes  in  line 

21 

18 

Rag  wheel 

18G 

24 

44  jigs 

31 

1 

Ram 

24 

60 

44  Object  of  hand 

21 

15 

“ of  a punching  machine  . . . 

29 

2 

44  stand 

20 

11 

Ratchet,  Drilling  crow  for 

21 

8 

Reciprocating  parts  of  an  en- 

“  drilling,  Use  of 

21 

6 

gine,  Fitting 

“ Old  man  for  use  with 

21 

8 

the 

23 

33 

“ Special  

21 

8 

44  parts,  Placing 

“ wrenches 

21 

26 

of,  on  vertical 

Ratchets,  Drilling. 

21 

6 

engine 

23 

43 

Ratio,  Velocity 

17 

1 

Recut  file 

20 

29 

Rawhide,  Lubricants  for  cut- 

Redrawing  

30 

14 

ting  

24 

43 

“ dies 

30 

28 

Reading  decimals 

25 

6 

44  Reverse 

30 

30 

Reamer,  Expanding 

26 

29 

Reeding 

30 

32 

“ grinding 

19 

47 

Reference  gauges 

28 

1 

INDEX 


XXXI 


Sec. 

Page 

Sec.  Page 

Releasing  die  holders 

26 

9 

Scraper,  Bent  or  hook 

21 

3 

“ tap  holders 

25 

36 

“ Flat 

21 

2 

Relief  of  taps 

25 

26 

Holding  of 

21 

4 

Rest,  Back,  for  grinding 

19 

28 

Three-cornered 

21 

2 

“ Fixed,  for  grinding 

19 

28 

Scrapers,  Forms  of 

21 

2 

“ Flexible  fixed,  for  grind- 

“ Use  of 

21 

1 

ing 

19 

29 

Scraping 

20 

29 

“ Follow,  for  grinding 

19 

28 

“ a plane  surface 

21 

5 

“ Rigid,  fixed,  for  grinding 

19 

28 

“ Marking  material 

“ Spring,  for  grinding 

19 

29 

used  in 

21 

5 

“ Universal  back,  for  grind- 

, “ plane 

28 

41 

ing 

19 

30 

“ Use  of  surface  plate 

Rests,  Special,  for  grinding 

19 

33 

in 

21 

5 

“ used  in  grinding,  Classi- 

Screw  heads 

24 

72 

fication  of 

19 

27 

“ vise 

20 

8 

Reverse  redrawing 

30 

30 

Screws,  Putting  in  wood 

24 

69 

Revolving  laying-out  plate 

21 

50 

Scriber 

20 

4 

Rigging : 

24 

1 

Seaming  dies 

30 

10 

Ring  gauge,  Making  an  in- 

Seasoning  lathe  beds 

23 

1 

serted-bushing 

28 

10 

Selection  of  a grinding  wheel 

19 

3 

“ gauges 

28 

6 

Self-centering  dies 

29 

17 

“ gauges.  Classes  of 

28 

8 

Seller’s  tool-grinding  machine 

186 

35 

“ gauges,  Laps  for 

28 

11 

Separator,  Oil 

24 

43 

“ gauges,  Proportions  of.. 

28 

11 

Set  wheel  method  of  grinding 

19 

26 

Robinson  odontograph 

17 

31 

Setting  engine  valves 

23 

36 

Rods,  Laying  out  ends  for 

“ planer  heads 

23 

19 

small 

21 

61 

Shafting 

24 

50 

Root  circle 

17 

6 

“ Grease  for 

24 

37 

“ diameter 

17 

5 

“ Horsepower  and  size 

“ or  dedendum 

17 

6 

of 

24 

51 

Rope  wheel,  Assembling  a 

“ Power  transmitted  by 

large 

22 

27 

cold-rolled  iron  line 

24 

53 

Ropes,  Inspection  of 

24 

4 

“ Power  transmitted  by 

“ Materials  used  for 

24 

6 

turned-iron  line 

24 

52 

Rose  reamers 

26 

26 

“ Power  transmitted  by 

Roughing,  Chucking  reamers 

turned-iron  head 

24 

50 

for 

26 

27 

Shaper,  Fellows  gear 

18 

23 

Round  file 

20 

33 

Sharpening  formed  cutters. . . . 

19 

61 

“ files,  Use  of 

20 

43 

Shear  of  a die 

29 

13 

“ keys 

20 

50 

“ of  dip  of  dies 

29 

32 

Rubber,  Cutting  soft 

24 

70 

Shell  reamers 

26 

25 

“ Working  vulcanized. . 

24 

70 

Shellac  wheels 

186 

12 

Running  fits,  Allowance  for.. . 

22 

35 

Short  splice 

24 

6 

Shrink  fits 

22 

29 

S 

Sec. 

Page 

“ fits 

22 

36 

Saddle,  Squaring  lathe,  with 

“ fits,  Allowance  for 

22 

37 

spindle 

23 

7 

“ fits,  Special  heater  for 

22 

38 

Safe-edged  file 

20 

29 

Side  chisel 

20 

18 

Sal  ammoniac,  Use  of,  in  gal- 

Silicate wheels 

186 

12 

vanizing 

24 

24 

Single-action  press 

30 

19 

Saws,  Hand  hack 

20 

6 

“ cut  file 

20 

30 

“ Power  hack 

20 

6 

Sizing  power  of  an  emery 

Scale  of  hardness 

186 

8 

wheel 

19 

27 

Scotch  drill 

21 

8 

Slings,  Inspection  of 

24 

4 

Scrap  heap 

24 

32 

“ Use  of 

24 

3 

“ or  wad  

29 

12 

Snap  gauges,  Advantages  of.. 

28 

15 

XXX11 


INDEX 


Sec. 


Snap  gauges,  Form  of 28 

“ gauges,  Making  of 28 

“ limit  gauges 28 

Socket  wrenches 21 

Soda  kettle 24 

Solutions,  Pickling 24 

Sparks,  Noting  of,  during 

grinding 19 

Special  gauges 28 

Speed,  Belt 24 

“ Cutting,  for  internal 

grinding 19 

“ of  grinding  wheel  and 

work 19 

Spindle,  Making  taper  holes  in 

headstock 23 

Spindles,  Boring  for  lathe 
head  stock  and 

tail-stock 23 

“ Lining  headstock 
and  tail-stock  of 

lathe 23 

Spiral  bevel  gears 18 

“ milling  cutters 27 

Splice,  Eye 24 

“ Long 24 

“ Making  a long 24 

“ Making  a short  24 

“ Making  an  eye 24 

“ Short 24 

Splices 24 

Splicing  instruments 24 

“ tools 24 

Spotting  of  work  in  grinding..  19 

Spring  die 26 

“ rest  for  grinding 19 

Spur  gear — 17 

“ gear  calculations,  Rules 

for 17 

“ gears 17 

Square  knot 24 

“ Laying  out  of 21 

“ Making  a try 28 

“ threaded  taps  25 

Squares,  Testing  try 28 

Squaring  tapped  holes 21 

Stand,  Filing 20 

“ Reaming 20 

Staybolt  tap,  Wrench  for 21 

Steady  rests,  Benefits  from  use 

of 19 

Steam  cylinders,  Lagging  of..  24 

“ pipes,  Lagging  of 24 

Steel,  Blackening  of 24 

“ Bluing  of 24 

“ Browning  of 24 


Sec.  Page 


Steel,  Lubricants  for  cutting. . 24  41 

“ Seasoning  of 28  5 

Step  reamer 21  15 

Stock,  Amount  of,  left  between 

holes  by  punches 29  23 

“ Economy  in  use  of,  in 

dies 29  21 

Stone  jacks — 22  11 

Stop-pins  for  jigs 31  15 

Stops  for  jigs 31  3 

Straight  peen  hammer 20  2 

“ reamers 26  11 

Straightedge,  Knife-edge 28  39 

“ Number  neces- 

sary to  origi- 
nate one 28  37 

“ Originating  a.. . 28  37 

Straightedges 21  40 


Finishing  the 
testing  edge  of  28  40 


“ Forms  of 28  38 

“ Hardening  of...  28  40 

“ Long 21  41 

Straightening  taps 25  25 

Strip,  Chipping.  20  24 

Strippers 29  10 

Stud-bolt  wrench 21  27 

Sulphuric  acid  for  pickling. .. . 24  19 

Surface  grinding 186  42 

“ grinding 19  45 

“ grinding  machine 19  46 

“ plate,  Use  of,  in  scra- 
ping   21  5 

“ plates 21  40 

“ Scraping  a plane 21  5 

Surfaces,  Chipping  a large  flat  20  22 

“ Lapping  of  plane 19  67 

Surfacing  machines,  Hand. . ..  18(9  28 

Swasey  gear-cutter 18  32 

Swivel  vise 20  9 

T Sec.  Page 

Table,  Placing  of  planer 23  15 

Tackle  block 22  39 

Tackles,  Handy 22  39 

Tail-stocks,  Boring  of  lathe  . 23  3 

“ stocks,  Machining  of  lathe  23  3 

Tanite  wheels 186  13 

Tap  holders,  Releasing 25  36 

“ Making  a hand 25  23 

“ wrench  for  staybolt 21  22 

Taper,  Different  definitions  of  28  22 

“ file 20  29 

“ gauge,  Laying  out  of.. . 28  24 

“ gauges 28  1 


Page 

15 

17 

16 

25 

18 

19 

13  r 

12 

48 

38 

8 

3 

4 

38 

4 

6 

6 

9 

7 

10 

6 

6 

7 

29 

6 

29 

3 

9 

1 

13 

45 

31 

33 

33 

19 

11 

11 

22 

27 

54 

54 

71 

70 

71 


index  xxxiii 


Sec. 

Page 

Sec.  Page 

Taper  gauges 

28 

22 

Teeth  gear,  Proportions  of, 

“ keys 

20 

50 

for  diametral  pitch. . . 

17 

9 

“ press  fits 

22 

34 

“ gear,  Space  of 

17 

6 

“ reamers 

26 

11 

44  gear,  Thickness  of 

17 

6 

“ reamers 

26 

23 

“ involute,  Base  circle  for 

17 

19 

“ reaming 

21 

16 

44  Laying  out  of  cycloidal 

17 

26 

“ taps 

25 

26 

44  Length  of 

17 

7 

41  taps,  Errors  in 

25 

27 

“ Octoidal  gear 

18 

29 

Tapers,  Originating 

28 

26 

44  of  broaches,  Angle  of 

21 

14 

Tapped  hole,  Squaring  of 

21 

19 

14  of  gears,  Calculating 

Tapping 

21 

18 

the  depth  of 

18 

8 

“ jig 

21 

20 

44  of  worm-wheel.  Depth 

“ jigs 

31 

1 

of 

17 

45 

“ pipe  threads 

21 

21 

44  Proportions  of  gear 

17 

8 

“ Production  of  smooth 

44  rack,  Grant’s  rule  for.. 

17 

25 

threads  in 

21 

20 

44  Width  of 

17 

7 

Taps,  Adjustable 

25 

30 

Temper  of  reamers 

26 

22 

“ Collapsing 

25 

33 

44  required  in  dies 

29 

8 

“ Cutting  thread  of,  with 

Temperature,  Influence  of,  on 

die  

25 

24 

grinding, 

19 

11 

“ Design  and  construction 

Tempering  dies 

29 

30 

of 

25 

21 

44  of  milling  cutters 

27 

3 

“ Design  of  collapsing. . . . 

25 

34 

44  the  punch 

29 

32 

“ Errors  in  taper 

25 

27 

Templet  for  symmetrical  work, 

“ for  brass,  Square-thread 

25 

38 

Filing 

29 

28 

“ for  square  threads 

25 

38 

44  Foundation  bolt 

22 

14 

“ Form  of  flutes  for 

25 

21 

“ Foundation  bolt  for 

44  Hand 

25 

23 

engine 

23 

37 

“ Hardening  of 

25 

25 

“ grinding  process  of 

“ Land  of 

25 

22 

gear-cutting 

18 

21 

44  Left-handed 

25 

33 

“ planing  process  o f 

44  Location  of  cutting  faces 

gear-cutting 

18 

3 

of 

25 

22 

44  planing  process  of 

44  Machine 

25 

26 

gear-cutting 

18 

20 

44  Making  of  collapsing. . . . 

25 

35 

Testing  emery  wheels 

18(7 

17 

44  Multiple-threaded 

25 

33 

44  lathe  beds 

23 

2 

44  Number  of,  necessary  in 

Thread  cutting,  Dies  for 

26 

1 

a set 

21 

21 

44  cutting,  Inside 

21 

18 

44  Number  of  flutes  for 

25 

21 

44  Effect  of  hardening  on 

44  Number  of,  required  in 

pitch  of 

25 

25 

special  cases 

25 

38 

“ worm,  Form  of 

17 

48 

44  Object  of  fluting 

25 

21 

Threading  pipe 

21 

31 

“ Relief  of 

25 

26 

Threads,  Production  of  smooth, 

4 Square-threaded 

25 

33 

in  tapping 

21 

20 

“ Straightening  of 

25 

25 

Three-cornered  scraper 

21 

2 

“ Taper 

25 

26 

Throat  diameter  of  a worm- 

Teeth,  Convergence  of  bevel 

wheel 

17 

45 

gear 

17 

35 

Timber  hitch 

24 

12 

“ Depth  of  cut  for 

Time  element  in  work 

24 

30 

gear 

18 

8 

Tinning 

24 

26 

“ for  milling  cutters, 

44  by  dipping  the  work 

Nicked 

27 

4 

into  molten  tin 

24 

26 

“ gear,  Depth  gauge  for 

18 

9 

44  by  the  cold  process 

24 

27 

“ gear,  Devices  for  draw- 

Tongs, Pipe 

21 

33 

ing 

17 

18 

Tool  cupboards 

24 

58 

“ gear,  Laying  out  of  — 

17 

17 

44  Forming 

27 

17 

XXXIV 


INDEX 


Sec. 


Tool  grinding 186 

“ grinding 19 

“ grinding  by  hand 186 

“ grinding  machine 186 


“ grinding  machine,  Gisholt  186 
“ grinding  machine,  Seller’s  186 


“ grinding  machine,  Wet. . . 186 

“ grinding,  Selection  of 

wheels  for 186 

“ Hob-forming 27 

“ racks 24 

“ rests  for  grindstones 186 

Toolmaker,  Work  of  the 25 

Toolmaking 25 

“ Limitations  of 25 

**  Special  tools  used 

in 25 

Tools,  Cheap  lubricant  for  cut- 
ting  24 

“ Construction  of 25 

“ Design  of. . : 25 

“ for  splicing 24 

“ Keeping  machine  - shop  24 

“ Lapping  diamond 19 

“ Laying  out 21 

“ Painting  machine 24 

“ Roller,  for  expanding 

metal  linings 24 

“ Speed  of  grindstone  in 

grinding 186 

“ used  in  toolmaking, 

Special 25 

Tooth,  Breadth  of 17 

“ curves  for  bevel  gears, 

Laying  out 17 

“ curves  in  general  use.. . 17 

“ Face  of.. 17 

“ Flank  of 17 

Tote  boxes 24 

Track  jacks 22 

Tram  for  engine 23 

Transmission  of  power 24 

Traveling  crane,  Electric 22 

“ crane,  Hand 22 

“ crane,  Power 22 

Trestles 22 

Triple-action  drawing  die 30 

Triplex  hoist 24 

Trolley  system  for  handling 

work 22 

Trucks,  Erecting 23 

Truing  emery  wheels 186 

“ grinding  wheels 19 

Try  square,  Making  a. 28 

“ squares 28 

“ squares,  Testing  of 28 


Sec.  Page 


Tube  squirting 30  35 

Turpentine 24  38 

“ as  a lubricant 24  43 

Twist  drill,  Multiple-lip 26  27 

U Sec.  Page 


Universal  back  rest  for  grinding  19  30 

“ grinding  machine  . . . 186  43 

“ grinding  machine  . . . 186  47 

V Sec.  Page 

Valve  gear,  Placing,  on  loco- 
motive   23  55 

“ seats,  Lapping  of 19  66 

“ setting 23  36 

Velocity  ratio 17  1 

“ ratio,  Constant,  i n 

gearing 17  7 

“ ratio  of  gears 17  14 

“ ratio  of  worm-wheels  17  44 

Vertical  engine,  Dismantling  a 23  44 

“ engine,  Oiling  devices 

for 23  44 

“ reaming,  Advantage 

of 21  17 

“ reaming,  Example  of  21  18 

“ stationary  engine, 

Erecting  a 23  41 

Vibration,  Absorption  of,  dur- 
ing grinding 19  33 

“ of  work,  Influence 
of,  on  grinding 

wheel 19  4 

Vise,  Cam  and  lever 20  8 

“ jaws 20  10 

“ jaws,  Protection  of  work 

from 20  10 

“ Pipe 20  9 

“ Rapid-motion 20  8 

“ Screw 20  8 

“ Swivel 20  9 

“ work,  Tools  used  in 20  2 

Vises,  Pipe 21  32 

“ Special  forms  of 20  11 

Vitrified  emery  wheels 186  12 

Volatile  oils 24  38 

Vulcanite  wheels 186  12 

W Sec.  Page 

Wad 29  12 

Walker  odontograph  chart  — 17  32 

Waste,  Disposition  of  greasy. . 24  40 

“ Use  of 24  40 

Water,  Action  of,  on  a grind- 
stone  186  2 


Page 

32 

47 

32 

34 

37 

35 

33 

38 

21 

59 

3 

7 

13 

14 

42 

3 

2 

7 

57 

68 

39 

28 

64 

5 

14 

7 

39 

18 

7 

7 

56 

11 

35 

45 

45 

43 

44 

2 

25 

5 

42 

24 

14 

10 

31 

31 

33 


INDEX 


XXXV 


Sec. 

Page 

Sec. 

Page 

Water  cut 

24 

41 

Wiring,  False 

30 

11 

Wheel, 

Combination  grinding 

19 

4 

Wooden  blocking 

22 

2 

“ 

cup,  Use  of,  in  grinding 

19 

55 

Woodruff  keys 

20 

50 

“ 

emery,  Parts  of 

186 

11 

Wood  screws,  Putting  in  of 

24 

69 

“ 

Grade  of  grinding 

19 

3 

Work,  Bench 

20 

1 

“ 

grinding,  Influence  of 

“ bench,  Post 

20 

16 

hardness  of  work  on 

19 

4 

“ benches 

20 

12 

“ 

grinding,  Relation  be- 

“ benches,  Permanent. . 

20 

13 

tween  grade  of,  and 

“ benches,  Portable 

20 

14 

work  

186 

25 

“ Centers  for  straighten- 

44 

grinding,  Selection  of 

19 

3 

ing  

20 

5 

“ 

Rag 

18  G 

24 

“ Cheapening  of,  by  dupli- 

“ 

Speed  of  grinding 

186 

18 

cation  

24 

29 

“ 

Speed  of,  in  grinding.. 

19 

8 

“ Chipping  of 

20 

19 

“ 

Worm 

17 

42 

“ Cleaning  of 

24 

18 

Wheels,  Brush 

18(7 

24 

“ Coating,  with  zinc 

24 

23 

“ 

Buffing 

186 

22 

“ Coatings  used  on  which 

“ 

Celluloid 

186 

13 

to  make  lines  on 

21 

38 

“ 

Directions  for  selec- 

“ Discharge  of,  from  dies 

30 

26 

tion  of  grinding 

19 

5 

“ Drawing,  with  tapered 

“ 

emery,  Bonds  for 

186 

11 

or  curved  walls 

30 

21 

44 

emery,  Bushing  of 

186 

13 

“ Driving,  between  cen- 

44 

emery,  Classification 

ters  on  grinding  ma- 

of   

186 

11 

chine  

19 

16 

“ 

emery,  Grading  of 

186 

15 

“ Filing  templet  for  sym- 

u 

emery,  Manufacture 

metrical 

29 

28 

of 

186 

11 

“ Finishing  filed 

20 

44 

“ 

emery,  Preparation  of 

186 

13 

“ Floor 

20 

1 

“ 

emery,  Testing  of 

186 

17 

“ Grinding  conical 

19 

21 

“ 

emery,  Truing  of 

186 

14 

“ Grinding  conical 

19 

42 

“ 

for  external  grinding, 

“ Grinding  cylindrical 

19 

18 

Selection  of 

19 

5 

“ Grinding  ends  of 

19 

18 

“ 

for  internal  grinding, 

“ Grinding  of,  on  face 

Selection  of 

19 

5 

plate 

19 

45 

“ 

for  tool  grinding,  Se- 

“  Height  of,  during  filing 

20 

45 

lection  of 

186 

38 

“ Holding  of,  during  sur- 

“ 

Glazing  of  grinding. . . 

186 

26 

face  grinding 

19 

47 

II 

Grading  of  grinding  . . 

186 

25 

“ Influence  of  hardness  of, 

“ 

Grinding 

186 

7 

on  grinding  wheel 

19 

4 

“ 

grinding,  Cause  of 

“ Influence  of  tempera- 

glazing in 

19 

3 

ture  of,  on  grinding.. 

19 

11 

it 

Leather 

186 

24 

“ Influenceof  vibrationof, 

it 

Polishing 

186 

20 

on  grinding 

19 

4 

“ 

Selection  of,  for  sur- 

“  Laying  out  of 

21 

36 

face  grinding 

19 

47 

“ Laying  out  plate  for 

tt 

Selection  of  grinding. . 

186 

25 

heavy 

21 

47 

“ 

Shapes  of  grinding 

19 

6 

“ Laying  out  plate  for 

“ 

Shellac 

186 

12 

light 

21 

45 

“ 

Silicate 

186 

12 

“ of  the  toolmaker 

25 

7 

“ 

Tanite 

186 

13 

“ Plate  for  laying  out  gen- 

tt 

Truing  grinding 

19 

10 

eral 

21 

49 

“ 

Vitrified 

186 

12 

“ Protection  of,  from  vise 

“ 

Vulcanite 

186 

12 

jaws 

20 

10 

Width  of  tooth 

17 

7 

“ Relation  between  grade 

Willis  odontograph 

17 

30 

of  wheel  and 

186 

25 

Wiring. 

30 

11 

, “ Soda  kettle  for  cleaning 

24 

18 

XXXVI 


INDEX 


Sec. 

Page 

Sec. 

Page 

Work,  Special  appliances  for 

Worm-wheels,  Cutting  of,  with 

laying  out 

21 

52 

formed  cutter 

18 

36 

“ Speed  of,  in  grinding. . . 

19 

8 

“ wheels,  Gashing  of 

18 

37 

“ Spotting  of,  in  grinding 

19 

29 

“ wheels,  Hobbing  of 

18 

37 

“ Spotting  of,  when  using 

“ wheels,  Kinds  of 

17 

41 

rest  in  grinding 

19 

29 

“ wheels,  Making 

18 

36 

“ Steadying  of,  while 

“ wheels,  Velocity  ratio  of 

17 

44 

grinding 

19 

27 

Wrench,  Alligator 

21 

34 

“ Testing  of,  with  lathe 

“ Double-end 

21 

21 

indicator 

25 

17 

“ for  staybolt  tap 

21 

22 

“ Time  element  in 

24 

30 

“ Special  double 

21 

22 

“ Tote  boxes  for 

24 

56 

“ Stud-bolt 

21 

27 

“ Tray  racks  for 

24 

56 

“ Use  of  rope  as  pipe  . . 

21 

35 

Working  gauges 

28 

2 

Wrenches,  Angle  of  single- 

Worm-calculations   

17 

46 

end  

21 

23 

“ Definition  of 

17 

41 

“ Ratchet 

21 

26 

“ Outside  diameter  of  ... . 

17 

47 

“ Pipe 

21 

33 

“ Pitch  diameter  of 

17 

46 

“ Single-end 

21 

23 

“ thread,  Form  of 

17 

48 

“ Socket 

21 

25 

“ wheel 

17 

42 

“ Solid-end 

21 

24 

“ wheel  calculations 

17 

44 

Wrought  iron,  Lubricants  for 

“ wheel,  Depth  of  tooth  of 

17 

45 

cutting 

24 

41 

“ wheel,  Hobbed 

17 

42 

j 

“ wheel  hobs 

27 

20 

Z 

Sec. 

Page 

“ wheel,  Throat  diameter 

Zinc,  Coating  work  with 

24 

23 

of 

17 

45 

“ Recovering  waste 

24 

24 

